---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Wed 01/04/23: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:06 AM - Re: Trutrak AP with Garmin GPS 18x 5Hz (D McFadyean) 2. 04:22 AM - Re: Trutrak AP with Garmin GPS 18x 5Hz (David Cripps) 3. 07:55 AM - Re: Trutrak AP with Garmin GPS 18x 5Hz (D McFadyean) 4. 08:48 AM - Re: Trutrak AP with Garmin GPS 18x 5Hz (David Cripps) 5. 09:30 AM - Re: Trutrak AP with Garmin GPS 18x 5Hz (Rowland Carson) 6. 02:30 PM - Re: Trutrak AP with Garmin GPS 18x 5Hz (Dpc) ________________________________ Message 1 _____________________________________ Time: 02:06:42 AM PST US From: D McFadyean Subject: Re: Europa-List: Trutrak AP with Garmin GPS 18x 5Hz I'd not seen before the clip on the servo arm; there was an earlier Factory 'fix' of Loctited replacement screws. Later servos have a stud and pinned locknut instead (I guess the stud is held in only by Loctite!). The control column stops should take priority, as the servo stops are proba bly too light to limit enthusiastic control movements by the pilot, but sho uld at least contain a runaway servo or some other breakage in the servo. I might have some spare stops (if I can find them). The stops are half-visib le and annotated 'F' in the photo at: TruTrak-RV10-Roll-Installation-Guide. pdf (bendixking.com) https://www.bendixking.com/content/dam/bendixking/en/d ocuments/document-lists/downloads-and-manuals/TruTrak-RV10-Roll-Installatio n-Guide.pdf The shear pin is merely a 6-32 screw with a short part of its length (where this crosses the interface between the mating arm and hub) necked and poli shed to the roots of the screw thread. My own servo is mounted towards the back of the Europa 'tunnel' and connect s to a horn bolted to the rear end of the roll torque tube. This area used to get hot under certain situations via heat from the stainless firewall an d no tunnel ventilation. Subsequently a 'fire blanket' (two thin layers of woven Kevlar with thin fibreglass loft insulation sandwiched between, rathe r like Orkotek) placed on the back of the firewall enabled cooler temperatu res. I've not heard of the standard under-seat servo location getting too h ot. Duncan McF. > On 03 January 2023 at 22:30 David Cripps wrote: > > > Thank you for the comprehensive reply, Duncan, and also for the repli es from Alan and Peter. I really appreciate the feedback. > > > > It seems that the Skymap III should work OK for us, despite its 0.5Hz data refresh rate. A bit of =98hunting=99 shouldn=99t re ally be a problem. We hadn=99t planned to have it fly a full route an d navigate itself around turning points. I had thought we=99d be manu ally changing the selected track at each turning point, and then lock the t racking to the new direction required. However, the Skymap III does have a =98Turn Anticipation=99 feature if we should in the future want it to follow a route, and not overshoot a waypoint. Do most people use it to follow a full track, and make all the waypoint turns? > > > > Good to know about the shear pin in the arm as a last resort! Do you have any drawing of the necked stainless pin that you got the LAA to agree to? > > > > The servo that I have came out of an old Europa and didn=99t se em to have any physical stops on the servo arm. It did, however, have the e xtra alloy =98clip=99 to secure the screw that attaches the arm to the servo. I=99ve seen that that clip was an LAA requirement too (see photo). For the physical stops, I did see on another forum something t hat looked like it would do the job on this servo (may even have been a Tru trak part). Does the LAA specify what these stops should look like or be ma de of? Should they be set so that the servo arm touches them at the same ti me as the control column reaches its full deflection (if not, then which st op should =98take priority=99 and be hit first)? Does anyone ha ve a photo of what the stops look like in their setup? I imagine them being mounted on the bolts that attach the servo motor to its mounting frame. > > > > My servo would be mounted under the pax seat per Mod 75, so there is not really any ventilation there. Is it worth adding a little cooling fan t o the seat locker to keep the air circulating around the servo? > > > > Many thanks for all the input! > > David > > i). The Trutrak will work on a Europa at 0.5Hz update frequency (i.e. every 2 seconds). Sometimes the AP will hunt gently (yesterday was a case in point, but there were sites yesterday that were GPS-jamming as well, so that might have been a cause' or possibly I have a too low torque setting t han optimal in order to limit servo overheating). If too many options of ou tput data are requested in the GPS NMEA output setup then there won't be en ough time to output all that data within a faster update period; the GPS se t will normally tell you if this is going to be the case. > > iii). The servo does not care about torque feedback. The servo will p rovide a force (torque) only up to the maximum value that has been preselec ted. > > iv). The Europa needs quite a high torque setting (10 or 12 from memo ry, which can on hot days plus a high 'activity' setting result in servo ov erheating and shutdown if you have a trigear with 'heated'/unventilated fus elage tunnel and depending where the servo is mounted). > > The pilot stick force required to overcome maximum torque will be app lied without even thinking about it and in any case there is a necked brass shear pin (comprising a modified 6-32 brass instrument mounting screw) in the servo arm that can be easily sheared (even without knowing it, and then you wonder why the AP is not tracking!). I agreed with LAA to replace this with a (necked) stainless steel pin in order to provide a little more stre ngth and haven't sheared it since. > > I also think that when the servo gets very hot (as above) it's intern al voltage regulator starts to shut down (as many are designed to do). Agai n, there is no way of knowing when this happens until realisation that the AP is not tracking! > > v). The LAA will insist upon the stops on the servo, although these s tops are not particularly robust and the set up would be better adjusted so that the stops never have to resist the pilot's stick inputs. > > Otherwise, the Trutrak system and its dynamics work extremely well an d can do a much better job than the pilot, especially in turbulent conditio ns. > > Have you found a setting on your Skymap that allows adjustment of the pre-emptive steering sensitivity (or "turn anticipation")? > > > > Duncan McF. > > > > > > On 03 January 2023 at 13:10 David Cripps wrote: > > > > > > So, I've slowly been making some progress on this, having mocke d up the whole system out of the aircraft. I have now been able to test it in the workshop and yesterday in a car (it needed to be moving to get a tra ck signal). See attached photo. However, I now have a couple more questions /observations! > > > > i) It seems that the Skymap III that I used in these tests work s in terms of making the servo move and display a track on the Trutrak, so that's progress! However, I note from the Skymap manual that it only gives its GPS info every 2 seconds, rather than the once every second that the Tr utrak recommends to avoid 'wandering'. Peter, in your post you mentioned th at you were using a Skymap III - have you ever had a problem with this (ass uming your A/P is the Trutrak Digitrak too)? Alan, is the Garmin 196 that y ou've mentioned as suitable, able to be set to give data at the 'once per s econd' rates, as from the manual it seems it may too default to once every 2 seconds? > > > > ii) I noticed when testing in the car, that when the track that was displayed in the Trutrak was close to what we were actually tracking ( as read from the Skymap), that the servo was more or less static, and moved in the correct direction when there was a small deviation between what was set on the Trutrak and what we were tracking. However, because our roads a re not straight, there were frequently occasions when the actual track from the Skymap was miles away from that set on the Trutrak. In that situation the servo went a bit crazy and rotated its arm by many more degrees than it could ever do in the plane. Is this to be expected in this rather 'offline ' mode? I can imagine that when the Trutrak senses that its control input i s not creating the sort of aircraft track change that it had expected, that it just moves the servo even further in order to try to get aircraft to do something? > > > > iii) Clearly my mock-up does not provide any sort of 'force fee dback' to the servo control arm (ie the arm is completely free to rotate as it likes). In an aircraft, would this be taken care of by aerodynamic feed back via the aileron torque tube? What happens to the servo when it reaches the full movement that the aileron would allow (the point when the control column hits its roll stops)? > > > > iv) I can imagine that I wouldn't want the servo ever applying full aileron to create a turn as that would make for a very violent manoeuv re! I see that there are settings that can be adjusted in the Trutrak set-u p menus that control activity level and also control maximum torque. What v alues have people set in theirs? I note that when I have set the recommende d value of 12 for the torque, it is almost impossible to override the servo arm when the A/P is engaged (though I appreciate that with no control colu mn attached the leverage I can apply to the servo arm with my fingers is ve ry low. I also appreciate that normally if one wanted to override the A/P y ou would disengage it first). > > > > v) Lastly (for now!) has anyone fitted physical 'stops' to the servo body that the servo arm would hit to ensure that the servo can never try to move the pushrod beyond the point where full aileron is applied? > > > > Apologies for all the questions but I want to make sure it is r eally working correctly before I contort myself to fit it into the aircraft itself! > > > > Best regards > > > > David > > > > On 19/11/2022, 16:26, "Alan Burrill" on behalf of alanb@dpy01.co.uk mailto:alanb@dpy01.co.uk > wrote: > > > > .uk mailto:alanb@dpy01.co.uk > > > > > > > Ok I=99ve had a. Ha ce to fly mine with the GPS feed off. > > > > > > As Duncan says below the display drops to show -|=94|- bu t maintains the track last set or you are holding when you switch it on. > > > > > > The are no heading digits on the display so you will need use y our compass/DI to show that. > > > > > > If you press the left or right =A4=B5=EF=B8=8F buttons then you can alter the track the AP is following either left or right and a numb er appears which if you press the button you can increase or decrease after the AP locks on the numbers disappear and you have the -|=94|- on th e display. > > > > > > Useful if you have a GPS failure but wouldn=99t want that as normal mode of operation so my suggestion is you need a GPS feed with t he right NEMA message set to get the most out of the AP and the ability for it to follow a track you have programmed in is a bonus. > > > > > > One word of caution, I have come across some GPS that don =99t put out any messages, even the position message for driving a Transpon der ADS-B output, unless there is a track in the GPS. That was how some of the older version worked, GARMIN 430 and possible the early AVMAP were guil ty of that. > > > > > > Hope that helps. > > > > > > Alan > > > > > > Sent from my iPad > > > > > > > > > > > > On 10 Nov 2022, at 10:52, D McFadyean > wrote: > > > yean@talktalk.net mailto:ami-mcfadyean@talktalk.net > > > > > > > Digitrak only needs basic positional information from the GPS on a regular basis. It will use this information to fly the track that has been set on the Digitrak. > > > If a route is programmed in to the GPS, it will fly that too (with different commands being set at the Digitrak control head to enab le this), so long as the GPS is also putting out the crosstrack error signa l; not all of them do. > > > > > > Duncan McF. > > > > > > > > > > > > > > > > > > s.com/Navigator?Europa-List> > > ion> > > > > > > > > > > > > > > > > > ________________________________ Message 2 _____________________________________ Time: 04:22:26 AM PST US Subject: Re: Europa-List: Trutrak AP with Garmin GPS 18x 5Hz From: David Cripps Thanks very much for this extra info, Duncan. If you can find that spare stop that would be great. I had seen a picture s imilar to the one you sent of the stops in another aircraft application. Following your comments about the shear pin, I think this is the small bras s screw located just above the main central cross-head screw that holds the control arm onto the servo in the photo I=99ve attached here? I looked at mi ne more closely and saw that the head of that brass screw appeared to be sli ghtly loose and with some tapping I could get the screw head to drop out of the arm. If that is the shear pin you=99re referring to then it appears mine is already sheared! However, the arm doesn=99t show any tendency to rotate on the hub? I guess the cross-head screw is holding it onto the hub pretty f irmly, but I can see that the arm could potentially rotate against the hub w ithout the pin being there (since there is no positive locking mechanism aga inst rotation), but the cross-head screw would need to be looser than it cur rently is for rotation of the arm to be possible. Should the arm be free to rotate against the hub without the pin there? Question also now is how to ge t the threaded bit out and the pin replaced?! Best regards David I'd not seen before the clip on the servo arm; there was an earlier Factory 'fix' of Loctited replacement screws. Later servos have a stud and pinned l ocknut instead (I guess the stud is held in only by Loctite!). The control column stops should take priority, as the servo stops are proba bly too light to limit enthusiastic control movements by the pilot, but shou ld at least contain a runaway servo or some other breakage in the servo. I m ight have some spare stops (if I can find them). The stops are half-visible and annotated 'F' in the photo at: TruTrak-RV10-Roll-Installation-Guide.pdf (bendixking.com) The shear pin is merely a 6-32 screw with a short part of its length (where this crosses the interface between the mating arm and hub) necked and polis hed to the roots of the screw thread. My own servo is mounted towards the back of the Europa 'tunnel' and connect s to a horn bolted to the rear end of the roll torque tube. This area used t o get hot under certain situations via heat from the stainless firewall and no tunnel ventilation. Subsequently a 'fire blanket' (two thin layers of wov en Kevlar with thin fibreglass loft insulation sandwiched between, rather li ke Orkotek) placed on the back of the firewall enabled cooler temperatures. I've not heard of the standard under-seat servo location getting too hot. Duncan McF. On 03 January 2023 at 22:30 David Cripps wrote: Thank you for the comprehensive reply, Duncan, and also for the replies fro m Alan and Peter. I really appreciate the feedback. It seems that the Skymap III should work OK for us, despite its 0.5Hz data refresh rate. A bit of =98hunting=99 shouldn=99t really be a problem. We had n=99t planned to have it fly a full route and navigate itself around turning points. I had thought we=99d be manually changing the selected track at eac h turning point, and then lock the tracking to the new direction required. H owever, the Skymap III does have a =98Turn Anticipation=99 feature if we sho uld in the future want it to follow a route, and not overshoot a waypoint. D o most people use it to follow a full track, and make all the waypoint turns ? Good to know about the shear pin in the arm as a last resort! Do you have a ny drawing of the necked stainless pin that you got the LAA to agree to? The servo that I have came out of an old Europa and didn=99t seem to have a ny physical stops on the servo arm. It did, however, have the extra alloy =98clip=99 to secure the screw that attaches the arm to the servo. I=99ve seen that that clip was an LAA requirement too (see photo). For the physical sto ps, I did see on another forum something that looked like it would do the jo b on this servo (may even have been a Trutrak part). Does the LAA specify wh at these stops should look like or be made of? Should they be set so that th e servo arm touches them at the same time as the control column reaches its full deflection (if not, then which stop should =98take priority=99 and be h it first)? Does anyone have a photo of what the stops look like in their set up? I imagine them being mounted on the bolts that attach the servo motor to its mounting frame. My servo would be mounted under the pax seat per Mod 75, so there is not re ally any ventilation there. Is it worth adding a little cooling fan to the s eat locker to keep the air circulating around the servo? Many thanks for all the input! David i). The Trutrak will work on a Europa at 0.5Hz update frequency (i.e. every 2 seconds). Sometimes the AP will hunt gently (yesterday was a case in poin t, but there were sites yesterday that were GPS-jamming as well, so that mig ht have been a cause' or possibly I have a too low torque setting than optim al in order to limit servo overheating). If too many options of output data are requested in the GPS NMEA output setup then there won't be enough time t o output all that data within a faster update period; the GPS set will norma lly tell you if this is going to be the case. iii). The servo does not care about torque feedback. The servo will provide a force (torque) only up to the maximum value that has been preselected. iv). The Europa needs quite a high torque setting (10 or 12 from memory, wh ich can on hot days plus a high 'activity' setting result in servo overheati ng and shutdown if you have a trigear with 'heated'/unventilated fuselage tu nnel and depending where the servo is mounted). The pilot stick force required to overcome maximum torque will be applied w ithout even thinking about it and in any case there is a necked brass shear pin (comprising a modified 6-32 brass instrument mounting screw) in the serv o arm that can be easily sheared (even without knowing it, and then you wond er why the AP is not tracking!). I agreed with LAA to replace this with a (n ecked) stainless steel pin in order to provide a little more strength and ha ven't sheared it since. I also think that when the servo gets very hot (as above) it's internal vol tage regulator starts to shut down (as many are designed to do). Again, ther e is no way of knowing when this happens until realisation that the AP is no t tracking! v). The LAA will insist upon the stops on the servo, although these stops a re not particularly robust and the set up would be better adjusted so that t he stops never have to resist the pilot's stick inputs. Otherwise, the Trutrak system and its dynamics work extremely well and can do a much better job than the pilot, especially in turbulent conditions. Have you found a setting on your Skymap that allows adjustment of the pre-e mptive steering sensitivity (or "turn anticipation")? Duncan McF. On 03 January 2023 at 13:10 David Cripps wrote: So, I've slowly been making some progress on this, having mocked up the who le system out of the aircraft. I have now been able to test it in the worksh op and yesterday in a car (it needed to be moving to get a track signal). Se e attached photo. However, I now have a couple more questions/observations! i) It seems that the Skymap III that I used in these tests works in terms o f making the servo move and display a track on the Trutrak, so that's progre ss! However, I note from the Skymap manual that it only gives its GPS info e very 2 seconds, rather than the once every second that the Trutrak recommend s to avoid 'wandering'. Peter, in your post you mentioned that you were usin g a Skymap III - have you ever had a problem with this (assuming your A/P is the Trutrak Digitrak too)? Alan, is the Garmin 196 that you've mentioned as suitable, able to be set to give data at the 'once per second' rates, as fr om the manual it seems it may too default to once every 2 seconds? ii) I noticed when testing in the car, that when the track that was display ed in the Trutrak was close to what we were actually tracking (as read from the Skymap), that the servo was more or less static, and moved in the correc t direction when there was a small deviation between what was set on the Tru trak and what we were tracking. However, because our roads are not straight, there were frequently occasions when the actual track from the Skymap was m iles away from that set on the Trutrak. In that situation the servo went a b it crazy and rotated its arm by many more degrees than it could ever do in t he plane. Is this to be expected in this rather 'offline' mode? I can imagin e that when the Trutrak senses that its control input is not creating the so rt of aircraft track change that it had expected, that it just moves the ser vo even further in order to try to get aircraft to do something? iii) Clearly my mock-up does not provide any sort of 'force feedback' to th e servo control arm (ie the arm is completely free to rotate as it likes). I n an aircraft, would this be taken care of by aerodynamic feedback via the a ileron torque tube? What happens to the servo when it reaches the full movem ent that the aileron would allow (the point when the control column hits its roll stops)? iv) I can imagine that I wouldn't want the servo ever applying full aileron to create a turn as that would make for a very violent manoeuvre! I see tha t there are settings that can be adjusted in the Trutrak set-up menus that c ontrol activity level and also control maximum torque. What values have peop le set in theirs? I note that when I have set the recommended value of 12 fo r the torque, it is almost impossible to override the servo arm when the A/P is engaged (though I appreciate that with no control column attached the le verage I can apply to the servo arm with my fingers is very low. I also appr eciate that normally if one wanted to override the A/P you would disengage i t first). v) Lastly (for now!) has anyone fitted physical 'stops' to the servo body t hat the servo arm would hit to ensure that the servo can never try to move t he pushrod beyond the point where full aileron is applied? Apologies for all the questions but I want to make sure it is really workin g correctly before I contort myself to fit it into the aircraft itself! Best regards David On 19/11/2022, 16:26, "Alan Burrill" on behalf of alanb@dpy01.c o.uk > wrote: alanb@dpy01.co.uk>> Ok I=99ve had a. Ha ce to fly mine with the GPS feed off. As Duncan says below the display drops to show -|=94|- but maintains the tr ack last set or you are holding when you switch it on. The are no heading digits on the display so you will need use your compass/ DI to show that. If you press the left or right =A4=B5=EF=B8=8F buttons then you can alter the track the AP is following either left or right and a number appears which if you p ress the button you can increase or decrease after the AP locks on the numbe rs disappear and you have the -|=94|- on the display. Useful if you have a GPS failure but wouldn=99t want that as normal mode of operation so my suggestion is you need a GPS feed with the right NEMA messa ge set to get the most out of the AP and the ability for it to follow a trac k you have programmed in is a bonus. One word of caution, I have come across some GPS that don=99t put out any m essages, even the position message for driving a Transponder ADS-B output, u nless there is a track in the GPS. That was how some of the older version wo rked, GARMIN 430 and possible the early AVMAP were guilty of that. Hope that helps. Alan Sent from my iPad On 10 Nov 2022, at 10:52, D McFadyean > wrote: > Digitrak only needs basic positional information from the GPS on a regular basis. It will use this information to fly the track that has been set on th e Digitrak. If a route is programmed in to the GPS, it will fly that too (with differen t commands being set at the Digitrak control head to enable this), so long a s the GPS is also putting out the crosstrack error signal; not all of them d o. Duncan McF. s.com/Navigator?Europa-List> ion> ________________________________ Message 3 _____________________________________ Time: 07:55:50 AM PST US From: D McFadyean Subject: Re: Europa-List: Trutrak AP with Garmin GPS 18x 5Hz With a failed pin, there would now be no shear connection between the servo hub and the arm other than friction. So, given enough torque it will slip, and it must have slipped at some point otherwise the pin wouldn't be shear ed. The earlier servos had a nylon washer under the crosshead screw to help it slip! I guess if you take off the arm, the remains of the shear pin may be projec ting from the hub sufficiently to get a grip on it. Duncan mcF. > On 04 January 2023 at 12:21 David Cripps wrote: > > > Thanks very much for this extra info, Duncan. > > > > If you can find that spare stop that would be great. I had seen a pic ture similar to the one you sent of the stops in another aircraft applicati on. > > > > Following your comments about the shear pin, I think this is the smal l brass screw located just above the main central cross-head screw that hol ds the control arm onto the servo in the photo I=99ve attached here? I looked at mine more closely and saw that the head of that brass screw app eared to be slightly loose and with some tapping I could get the screw head to drop out of the arm. If that is the shear pin you=99re referring to then it appears mine is already sheared! However, the arm doesn=99 t show any tendency to rotate on the hub? I guess the cross-head screw is h olding it onto the hub pretty firmly, but I can see that the arm could pote ntially rotate against the hub without the pin being there (since there is no positive locking mechanism against rotation), but the cross-head screw w ould need to be looser than it currently is for rotation of the arm to be p ossible. Should the arm be free to rotate against the hub without the pin t here? Question also now is how to get the threaded bit out and the pin repl aced?! > > > > Best regards > > > > David > > > > I'd not seen before the clip on the servo arm; there was an earlier F actory 'fix' of Loctited replacement screws. Later servos have a stud and p inned locknut instead (I guess the stud is held in only by Loctite!). > > The control column stops should take priority, as the servo stops are probably too light to limit enthusiastic control movements by the pilot, b ut should at least contain a runaway servo or some other breakage in the se rvo. I might have some spare stops (if I can find them). The stops are half -visible and annotated 'F' in the photo at: TruTrak-RV10-Roll-Installation- Guide.pdf (bendixking.com) https://www.bendixking.com/content/dam/bendixkin g/en/documents/document-lists/downloads-and-manuals/TruTrak-RV10-Roll-Insta llation-Guide.pdf > > The shear pin is merely a 6-32 screw with a short part of its length (where this crosses the interface between the mating arm and hub) necked an d polished to the roots of the screw thread. > > My own servo is mounted towards the back of the Europa 'tunnel' and c onnects to a horn bolted to the rear end of the roll torque tube. This area used to get hot under certain situations via heat from the stainless firew all and no tunnel ventilation. Subsequently a 'fire blanket' (two thin laye rs of woven Kevlar with thin fibreglass loft insulation sandwiched between, rather like Orkotek) placed on the back of the firewall enabled cooler tem peratures. I've not heard of the standard under-seat servo location getting too hot. > > > > Duncan McF. > > > > > > On 03 January 2023 at 22:30 David Cripps wrote: > > > > Thank you for the comprehensive reply, Duncan, and also for the replies from Alan and Peter. I really appreciate the feedback. > > > > > > > > It seems that the Skymap III should work OK for us, despite its 0.5Hz data refresh rate. A bit of =98hunting=99 shouldn =99t really be a problem. We hadn=99t planned to have it fly a full r oute and navigate itself around turning points. I had thought we=99d be manually changing the selected track at each turning point, and then loc k the tracking to the new direction required. However, the Skymap III does have a =98Turn Anticipation=99 feature if we should in the futu re want it to follow a route, and not overshoot a waypoint. Do most people use it to follow a full track, and make all the waypoint turns? > > > > > > > > Good to know about the shear pin in the arm as a last resort! D o you have any drawing of the necked stainless pin that you got the LAA to agree to? > > > > > > > > The servo that I have came out of an old Europa and didn =99t seem to have any physical stops on the servo arm. It did, however, hav e the extra alloy =98clip=99 to secure the screw that attaches the arm to the servo. I=99ve seen that that clip was an LAA requireme nt too (see photo). For the physical stops, I did see on another forum some thing that looked like it would do the job on this servo (may even have bee n a Trutrak part). Does the LAA specify what these stops should look like o r be made of? Should they be set so that the servo arm touches them at the same time as the control column reaches its full deflection (if not, then w hich stop should =98take priority=99 and be hit first)? Does an yone have a photo of what the stops look like in their setup? I imagine the m being mounted on the bolts that attach the servo motor to its mounting fr ame. > > > > > > > > My servo would be mounted under the pax seat per Mod 75, so the re is not really any ventilation there. Is it worth adding a little cooling fan to the seat locker to keep the air circulating around the servo? > > > > > > > > Many thanks for all the input! > > > > David > > > > i). The Trutrak will work on a Europa at 0.5Hz update frequency (i.e. every 2 seconds). Sometimes the AP will hunt gently (yesterday was a case in point, but there were sites yesterday that were GPS-jamming as wel l, so that might have been a cause' or possibly I have a too low torque set ting than optimal in order to limit servo overheating). If too many options of output data are requested in the GPS NMEA output setup then there won't be enough time to output all that data within a faster update period; the GPS set will normally tell you if this is going to be the case. > > > > iii). The servo does not care about torque feedback. The servo will provide a force (torque) only up to the maximum value that has been pr eselected. > > > > iv). The Europa needs quite a high torque setting (10 or 12 fro m memory, which can on hot days plus a high 'activity' setting result in se rvo overheating and shutdown if you have a trigear with 'heated'/unventilat ed fuselage tunnel and depending where the servo is mounted). > > > > The pilot stick force required to overcome maximum torque will be applied without even thinking about it and in any case there is a necked brass shear pin (comprising a modified 6-32 brass instrument mounting scre w) in the servo arm that can be easily sheared (even without knowing it, an d then you wonder why the AP is not tracking!). I agreed with LAA to replac e this with a (necked) stainless steel pin in order to provide a little mor e strength and haven't sheared it since. > > > > I also think that when the servo gets very hot (as above) it's internal voltage regulator starts to shut down (as many are designed to do) . Again, there is no way of knowing when this happens until realisation tha t the AP is not tracking! > > > > v). The LAA will insist upon the stops on the servo, although t hese stops are not particularly robust and the set up would be better adjus ted so that the stops never have to resist the pilot's stick inputs. > > > > Otherwise, the Trutrak system and its dynamics work extremely w ell and can do a much better job than the pilot, especially in turbulent co nditions. > > > > Have you found a setting on your Skymap that allows adjustment of the pre-emptive steering sensitivity (or "turn anticipation")? > > > > > > > > Duncan McF. > > > > > > > > > > On 03 January 2023 at 13:10 David Cripps wrote: > > > > > > > > > So, I've slowly been making some progress on this, having mocked up the whole system out of the aircraft. I have now been able to te st it in the workshop and yesterday in a car (it needed to be moving to get a track signal). See attached photo. However, I now have a couple more que stions/observations! > > > > > > i) It seems that the Skymap III that I used in these test s works in terms of making the servo move and display a track on the Trutra k, so that's progress! However, I note from the Skymap manual that it only gives its GPS info every 2 seconds, rather than the once every second that the Trutrak recommends to avoid 'wandering'. Peter, in your post you mentio ned that you were using a Skymap III - have you ever had a problem with thi s (assuming your A/P is the Trutrak Digitrak too)? Alan, is the Garmin 196 that you've mentioned as suitable, able to be set to give data at the 'once per second' rates, as from the manual it seems it may too default to once every 2 seconds? > > > > > > ii) I noticed when testing in the car, that when the trac k that was displayed in the Trutrak was close to what we were actually trac king (as read from the Skymap), that the servo was more or less static, and moved in the correct direction when there was a small deviation between wh at was set on the Trutrak and what we were tracking. However, because our r oads are not straight, there were frequently occasions when the actual trac k from the Skymap was miles away from that set on the Trutrak. In that situ ation the servo went a bit crazy and rotated its arm by many more degrees t han it could ever do in the plane. Is this to be expected in this rather 'o ffline' mode? I can imagine that when the Trutrak senses that its control i nput is not creating the sort of aircraft track change that it had expected , that it just moves the servo even further in order to try to get aircraft to do something? > > > > > > iii) Clearly my mock-up does not provide any sort of 'for ce feedback' to the servo control arm (ie the arm is completely free to rot ate as it likes). In an aircraft, would this be taken care of by aerodynami c feedback via the aileron torque tube? What happens to the servo when it r eaches the full movement that the aileron would allow (the point when the c ontrol column hits its roll stops)? > > > > > > iv) I can imagine that I wouldn't want the servo ever app lying full aileron to create a turn as that would make for a very violent m anoeuvre! I see that there are settings that can be adjusted in the Trutrak set-up menus that control activity level and also control maximum torque. What values have people set in theirs? I note that when I have set the reco mmended value of 12 for the torque, it is almost impossible to override the servo arm when the A/P is engaged (though I appreciate that with no contro l column attached the leverage I can apply to the servo arm with my fingers is very low. I also appreciate that normally if one wanted to override the A/P you would disengage it first). > > > > > > v) Lastly (for now!) has anyone fitted physical 'stops' t o the servo body that the servo arm would hit to ensure that the servo can never try to move the pushrod beyond the point where full aileron is applie d? > > > > > > Apologies for all the questions but I want to make sure i t is really working correctly before I contort myself to fit it into the ai rcraft itself! > > > > > > Best regards > > > > > > David > > > > > > On 19/11/2022, 16:26, "Alan Burrill" on behalf of alanb@dpy01.co.uk mailto:alanb@dpy01.co.uk > wrote: > > > > > > y01.co.uk mailto:alanb@dpy01.co.uk > > > > > > > > > > Ok I=99ve had a. Ha ce to fly mine with the GPS fee d off. > > > > > > > > > As Duncan says below the display drops to show -| =94|- but maintains the track last set or you are holding when you switch i t on. > > > > > > > > > The are no heading digits on the display so you will need use your compass/DI to show that. > > > > > > > > > If you press the left or right =A4=B5=EF=B8=8F buttons then you can alter the track the AP is following either left or right and a number appears which if you press the button you can increase or decrease after the AP locks on the numbers disappear and you have the -|=94|- on the display. > > > > > > > > > Useful if you have a GPS failure but wouldn=99t wan t that as normal mode of operation so my suggestion is you need a GPS feed with the right NEMA message set to get the most out of the AP and the abili ty for it to follow a track you have programmed in is a bonus. > > > > > > > > > One word of caution, I have come across some GPS that don =99t put out any messages, even the position message for driving a Tr ansponder ADS-B output, unless there is a track in the GPS. That was how so me of the older version worked, GARMIN 430 and possible the early AVMAP wer e guilty of that. > > > > > > > > > Hope that helps. > > > > > > > > > Alan > > > > > > > > > Sent from my iPad > > > > > > > > > > > > > > On 10 Nov 2022, at 10:52, D McFadyean > wrote: > > > > -mcfadyean@talktalk.net mailto:ami-mcfadyean@talktalk.net > > > > > > > > > Digitrak only needs basic positional information fr om the GPS on a regular basis. It will use this information to fly the trac k that has been set on the Digitrak. > > > > If a route is programmed in to the GPS, it will fly that too (with different commands being set at the Digitrak control head t o enable this), so long as the GPS is also putting out the crosstrack error signal; not all of them do. > > > > > > > > Duncan McF. > > > > > > > > > > > > > > > > > > > > > > > > > > s.com/Navigator?Europa-List> > > > ion> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ________________________________ Message 4 _____________________________________ Time: 08:48:13 AM PST US Subject: Re: Europa-List: Trutrak AP with Garmin GPS 18x 5Hz From: David Cripps Thanks, Duncan. I have removed the arm now (and the crosshead screw does indeed have a nylo n washer under it). I note the LAA requirement that this screw needs Loctiti ng when it is put back in, as well as the screw retaining clip refitting ove r it. I can see that the shaft of the brass pin has broken below the surface of t he hub so unfortunately there is nothing to grab onto. However, I also notic e that there are two other similar screw holes in the hub which could be use d instead, by rotating the hub through 120deg. Perhaps this is a deliberate design to give a chance of doing an in-field replacement of a sheared pin in order to get it working again, enabling the removal of the old pin stub to be done at a later time. Any ideas how to remove that stub? I have some screw extractors but they=99 re much too big. Also, do you know where I can obtain replacement pins? You probably made yo ur own when you switched to the stainless screws? If I do the same with a br ass or stainless 6-32 screw is there a defined amount of =98necking=99 requi red so that it shears at an appropriate shear force? David With a failed pin, there would now be no shear connection between the servo hub and the arm other than friction. So, given enough torque it will slip, and it must have slipped at some point otherwise the pin wouldn't be sheared . The earlier servos had a nylon washer under the crosshead screw to help it slip! I guess if you take off the arm, the remains of the shear pin may be projec ting from the hub sufficiently to get a grip on it. Duncan mcF. On 04 January 2023 at 12:21 David Cripps wrote: Thanks very much for this extra info, Duncan. If you can find that spare stop that would be great. I had seen a picture s imilar to the one you sent of the stops in another aircraft application. Following your comments about the shear pin, I think this is the small bras s screw located just above the main central cross-head screw that holds the control arm onto the servo in the photo I=99ve attached here? I looked at mi ne more closely and saw that the head of that brass screw appeared to be sli ghtly loose and with some tapping I could get the screw head to drop out of the arm. If that is the shear pin you=99re referring to then it appears mine is already sheared! However, the arm doesn=99t show any tendency to rotate on the hub? I guess the cross-head screw is holding it onto the hub pretty f irmly, but I can see that the arm could potentially rotate against the hub w ithout the pin being there (since there is no positive locking mechanism aga inst rotation), but the cross-head screw would need to be looser than it cur rently is for rotation of the arm to be possible. Should the arm be free to rotate against the hub without the pin there? Question also now is how to ge t the threaded bit out and the pin replaced?! Best regards David I'd not seen before the clip on the servo arm; there was an earlier Factory 'fix' of Loctited replacement screws. Later servos have a stud and pinned l ocknut instead (I guess the stud is held in only by Loctite!). The control column stops should take priority, as the servo stops are proba bly too light to limit enthusiastic control movements by the pilot, but shou ld at least contain a runaway servo or some other breakage in the servo. I m ight have some spare stops (if I can find them). The stops are half-visible and annotated 'F' in the photo at: TruTrak-RV10-Roll-Installation-Guide.pdf (bendixking.com) The shear pin is merely a 6-32 screw with a short part of its length (where this crosses the interface between the mating arm and hub) necked and polis hed to the roots of the screw thread. My own servo is mounted towards the back of the Europa 'tunnel' and connect s to a horn bolted to the rear end of the roll torque tube. This area used t o get hot under certain situations via heat from the stainless firewall and no tunnel ventilation. Subsequently a 'fire blanket' (two thin layers of wov en Kevlar with thin fibreglass loft insulation sandwiched between, rather li ke Orkotek) placed on the back of the firewall enabled cooler temperatures. I've not heard of the standard under-seat servo location getting too hot. Duncan McF. On 03 January 2023 at 22:30 David Cripps wrote: Thank you for the comprehensive reply, Duncan, and also for the replies fro m Alan and Peter. I really appreciate the feedback. It seems that the Skymap III should work OK for us, despite its 0.5Hz data refresh rate. A bit of =98hunting=99 shouldn=99t really be a problem. We had n=99t planned to have it fly a full route and navigate itself around turning points. I had thought we=99d be manually changing the selected track at eac h turning point, and then lock the tracking to the new direction required. H owever, the Skymap III does have a =98Turn Anticipation=99 feature if we sho uld in the future want it to follow a route, and not overshoot a waypoint. D o most people use it to follow a full track, and make all the waypoint turns ? Good to know about the shear pin in the arm as a last resort! Do you have a ny drawing of the necked stainless pin that you got the LAA to agree to? The servo that I have came out of an old Europa and didn=99t seem to have a ny physical stops on the servo arm. It did, however, have the extra alloy =98clip=99 to secure the screw that attaches the arm to the servo. I=99ve seen that that clip was an LAA requirement too (see photo). For the physical sto ps, I did see on another forum something that looked like it would do the jo b on this servo (may even have been a Trutrak part). Does the LAA specify wh at these stops should look like or be made of? Should they be set so that th e servo arm touches them at the same time as the control column reaches its full deflection (if not, then which stop should =98take priority=99 and be h it first)? Does anyone have a photo of what the stops look like in their set up? I imagine them being mounted on the bolts that attach the servo motor to its mounting frame. My servo would be mounted under the pax seat per Mod 75, so there is not re ally any ventilation there. Is it worth adding a little cooling fan to the s eat locker to keep the air circulating around the servo? Many thanks for all the input! David i). The Trutrak will work on a Europa at 0.5Hz update frequency (i.e. every 2 seconds). Sometimes the AP will hunt gently (yesterday was a case in poin t, but there were sites yesterday that were GPS-jamming as well, so that mig ht have been a cause' or possibly I have a too low torque setting than optim al in order to limit servo overheating). If too many options of output data are requested in the GPS NMEA output setup then there won't be enough time t o output all that data within a faster update period; the GPS set will norma lly tell you if this is going to be the case. iii). The servo does not care about torque feedback. The servo will provide a force (torque) only up to the maximum value that has been preselected. iv). The Europa needs quite a high torque setting (10 or 12 from memory, wh ich can on hot days plus a high 'activity' setting result in servo overheati ng and shutdown if you have a trigear with 'heated'/unventilated fuselage tu nnel and depending where the servo is mounted). The pilot stick force required to overcome maximum torque will be applied w ithout even thinking about it and in any case there is a necked brass shear pin (comprising a modified 6-32 brass instrument mounting screw) in the serv o arm that can be easily sheared (even without knowing it, and then you wond er why the AP is not tracking!). I agreed with LAA to replace this with a (n ecked) stainless steel pin in order to provide a little more strength and ha ven't sheared it since. I also think that when the servo gets very hot (as above) it's internal vol tage regulator starts to shut down (as many are designed to do). Again, ther e is no way of knowing when this happens until realisation that the AP is no t tracking! v). The LAA will insist upon the stops on the servo, although these stops a re not particularly robust and the set up would be better adjusted so that t he stops never have to resist the pilot's stick inputs. Otherwise, the Trutrak system and its dynamics work extremely well and can do a much better job than the pilot, especially in turbulent conditions. Have you found a setting on your Skymap that allows adjustment of the pre-e mptive steering sensitivity (or "turn anticipation")? Duncan McF. On 03 January 2023 at 13:10 David Cripps wrote: So, I've slowly been making some progress on this, having mocked up the who le system out of the aircraft. I have now been able to test it in the worksh op and yesterday in a car (it needed to be moving to get a track signal). Se e attached photo. However, I now have a couple more questions/observations! i) It seems that the Skymap III that I used in these tests works in terms o f making the servo move and display a track on the Trutrak, so that's progre ss! However, I note from the Skymap manual that it only gives its GPS info e very 2 seconds, rather than the once every second that the Trutrak recommend s to avoid 'wandering'. Peter, in your post you mentioned that you were usin g a Skymap III - have you ever had a problem with this (assuming your A/P is the Trutrak Digitrak too)? Alan, is the Garmin 196 that you've mentioned as suitable, able to be set to give data at the 'once per second' rates, as fr om the manual it seems it may too default to once every 2 seconds? ii) I noticed when testing in the car, that when the track that was display ed in the Trutrak was close to what we were actually tracking (as read from the Skymap), that the servo was more or less static, and moved in the correc t direction when there was a small deviation between what was set on the Tru trak and what we were tracking. However, because our roads are not straight, there were frequently occasions when the actual track from the Skymap was m iles away from that set on the Trutrak. In that situation the servo went a b it crazy and rotated its arm by many more degrees than it could ever do in t he plane. Is this to be expected in this rather 'offline' mode? I can imagin e that when the Trutrak senses that its control input is not creating the so rt of aircraft track change that it had expected, that it just moves the ser vo even further in order to try to get aircraft to do something? iii) Clearly my mock-up does not provide any sort of 'force feedback' to th e servo control arm (ie the arm is completely free to rotate as it likes). I n an aircraft, would this be taken care of by aerodynamic feedback via the a ileron torque tube? What happens to the servo when it reaches the full movem ent that the aileron would allow (the point when the control column hits its roll stops)? iv) I can imagine that I wouldn't want the servo ever applying full aileron to create a turn as that would make for a very violent manoeuvre! I see tha t there are settings that can be adjusted in the Trutrak set-up menus that c ontrol activity level and also control maximum torque. What values have peop le set in theirs? I note that when I have set the recommended value of 12 fo r the torque, it is almost impossible to override the servo arm when the A/P is engaged (though I appreciate that with no control column attached the le verage I can apply to the servo arm with my fingers is very low. I also appr eciate that normally if one wanted to override the A/P you would disengage i t first). v) Lastly (for now!) has anyone fitted physical 'stops' to the servo body t hat the servo arm would hit to ensure that the servo can never try to move t he pushrod beyond the point where full aileron is applied? Apologies for all the questions but I want to make sure it is really workin g correctly before I contort myself to fit it into the aircraft itself! Best regards David On 19/11/2022, 16:26, "Alan Burrill" on behalf of alanb@dpy01.c o.uk > wrote: alanb@dpy01.co.uk>> Ok I=99ve had a. Ha ce to fly mine with the GPS feed off. As Duncan says below the display drops to show -|=94|- but maintains the tr ack last set or you are holding when you switch it on. The are no heading digits on the display so you will need use your compass/ DI to show that. If you press the left or right =A4=B5=EF=B8=8F buttons then you can alter the track the AP is following either left or right and a number appears which if you p ress the button you can increase or decrease after the AP locks on the numbe rs disappear and you have the -|=94|- on the display. Useful if you have a GPS failure but wouldn=99t want that as normal mode of operation so my suggestion is you need a GPS feed with the right NEMA messa ge set to get the most out of the AP and the ability for it to follow a trac k you have programmed in is a bonus. One word of caution, I have come across some GPS that don=99t put out any m essages, even the position message for driving a Transponder ADS-B output, u nless there is a track in the GPS. That was how some of the older version wo rked, GARMIN 430 and possible the early AVMAP were guilty of that. Hope that helps. Alan Sent from my iPad On 10 Nov 2022, at 10:52, D McFadyean > wrote: > Digitrak only needs basic positional information from the GPS on a regular basis. It will use this information to fly the track that has been set on th e Digitrak. If a route is programmed in to the GPS, it will fly that too (with differen t commands being set at the Digitrak control head to enable this), so long a s the GPS is also putting out the crosstrack error signal; not all of them d o. Duncan McF. s.com/Navigator?Europa-List> ion> ________________________________ Message 5 _____________________________________ Time: 09:30:34 AM PST US From: Rowland Carson Subject: Re: Europa-List: Trutrak AP with Garmin GPS 18x 5Hz David - I found out the hard way about that shear screw - see my build journal at on 21st & 30th of the month. As you will see, I got my replacement shear screws direct from TruTrak. I don=99t seem to have a picture of it, but I seem to recall that there are several tapped holes that can be used for the screw so it=99 s not essential to remove the broken end. in friendship Rowland > On 2023-01-04, at 16:47, David Cripps wrote: > > Thanks, Duncan. > > I have removed the arm now (and the crosshead screw does indeed have a nylon washer under it). I note the LAA requirement that this screw needs Loctiting when it is put back in, as well as the screw retaining clip refitting over it. > > I can see that the shaft of the brass pin has broken below the surface of the hub so unfortunately there is nothing to grab onto. However, I also notice that there are two other similar screw holes in the hub which could be used instead, by rotating the hub through 120deg. Perhaps this is a deliberate design to give a chance of doing an in-field replacement of a sheared pin in order to get it working again, enabling the removal of the old pin stub to be done at a later time. > > Any ideas how to remove that stub? I have some screw extractors but they=99re much too big. > > Also, do you know where I can obtain replacement pins? You probably made your own when you switched to the stainless screws? If I do the same with a brass or stainless 6-32 screw is there a defined amount of =98necking=99 required so that it shears at an appropriate shear force? > > David > > > > With a failed pin, there would now be no shear connection between the servo hub and the arm other than friction. So, given enough torque it will slip, and it must have slipped at some point otherwise the pin wouldn't be sheared. The earlier servos had a nylon washer under the crosshead screw to help it slip! > > I guess if you take off the arm, the remains of the shear pin may be projecting from the hub sufficiently to get a grip on it. > > > > Duncan mcF. > > On 04 January 2023 at 12:21 David Cripps > wrote: > > Thanks very much for this extra info, Duncan. > > > > If you can find that spare stop that would be great. I had seen a picture similar to the one you sent of the stops in another aircraft application. > > > > Following your comments about the shear pin, I think this is the small brass screw located just above the main central cross-head screw that holds the control arm onto the servo in the photo I=99ve attached here? I looked at mine more closely and saw that the head of that brass screw appeared to be slightly loose and with some tapping I could get the screw head to drop out of the arm. If that is the shear pin you=99 re referring to then it appears mine is already sheared! However, the arm doesn=99t show any tendency to rotate on the hub? I guess the cross-head screw is holding it onto the hub pretty firmly, but I can see that the arm could potentially rotate against the hub without the pin being there (since there is no positive locking mechanism against rotation), but the cross-head screw would need to be looser than it currently is for rotation of the arm to be possible. Should the arm be free to rotate against the hub without the pin there? Question also now is how to get the threaded bit out and the pin replaced?! > > > > Best regards > > > > David > > > > I'd not seen before the clip on the servo arm; there was an earlier Factory 'fix' of Loctited replacement screws. Later servos have a stud and pinned locknut instead (I guess the stud is held in only by Loctite!). > > The control column stops should take priority, as the servo stops are probably too light to limit enthusiastic control movements by the pilot, but should at least contain a runaway servo or some other breakage in the servo. I might have some spare stops (if I can find them). The stops are half-visible and annotated 'F' in the photo at: TruTrak-RV10-Roll-Installation-Guide.pdf (bendixking.com) > The shear pin is merely a 6-32 screw with a short part of its length (where this crosses the interface between the mating arm and hub) necked and polished to the roots of the screw thread. > > My own servo is mounted towards the back of the Europa 'tunnel' and connects to a horn bolted to the rear end of the roll torque tube. This area used to get hot under certain situations via heat from the stainless firewall and no tunnel ventilation. Subsequently a 'fire blanket' (two thin layers of woven Kevlar with thin fibreglass loft insulation sandwiched between, rather like Orkotek) placed on the back of the firewall enabled cooler temperatures. I've not heard of the standard under-seat servo location getting too hot. > > > > Duncan McF. > > On 03 January 2023 at 22:30 David Cripps > wrote: > > Thank you for the comprehensive reply, Duncan, and also for the replies from Alan and Peter. I really appreciate the feedback. > > > > It seems that the Skymap III should work OK for us, despite its 0.5Hz data refresh rate. A bit of =98hunting=99 shouldn=99t really be a problem. We hadn=99t planned to have it fly a full route and navigate itself around turning points. I had thought we=99 d be manually changing the selected track at each turning point, and then lock the tracking to the new direction required. However, the Skymap III does have a =98Turn Anticipation=99 feature if we should in the future want it to follow a route, and not overshoot a waypoint. Do most people use it to follow a full track, and make all the waypoint turns? > > > > Good to know about the shear pin in the arm as a last resort! Do you have any drawing of the necked stainless pin that you got the LAA to agree to? > > > > The servo that I have came out of an old Europa and didn=99t seem to have any physical stops on the servo arm. It did, however, have the extra alloy =98clip=99 to secure the screw that attaches the arm to the servo. I=99ve seen that that clip was an LAA requirement too (see photo). For the physical stops, I did see on another forum something that looked like it would do the job on this servo (may even have been a Trutrak part). Does the LAA specify what these stops should look like or be made of? Should they be set so that the servo arm touches them at the same time as the control column reaches its full deflection (if not, then which stop should =98take priority=99 and be hit first)? Does anyone have a photo of what the stops look like in their setup? I imagine them being mounted on the bolts that attach the servo motor to its mounting frame. > > > > My servo would be mounted under the pax seat per Mod 75, so there is not really any ventilation there. Is it worth adding a little cooling fan to the seat locker to keep the air circulating around the servo? > > > > Many thanks for all the input! > > David > > i). The Trutrak will work on a Europa at 0.5Hz update frequency (i.e. every 2 seconds). Sometimes the AP will hunt gently (yesterday was a case in point, but there were sites yesterday that were GPS-jamming as well, so that might have been a cause' or possibly I have a too low torque setting than optimal in order to limit servo overheating). If too many options of output data are requested in the GPS NMEA output setup then there won't be enough time to output all that data within a faster update period; the GPS set will normally tell you if this is going to be the case. > > iii). The servo does not care about torque feedback. The servo will provide a force (torque) only up to the maximum value that has been preselected. > > iv). The Europa needs quite a high torque setting (10 or 12 from memory, which can on hot days plus a high 'activity' setting result in servo overheating and shutdown if you have a trigear with 'heated'/unventilated fuselage tunnel and depending where the servo is mounted). > > The pilot stick force required to overcome maximum torque will be applied without even thinking about it and in any case there is a necked brass shear pin (comprising a modified 6-32 brass instrument mounting screw) in the servo arm that can be easily sheared (even without knowing it, and then you wonder why the AP is not tracking!). I agreed with LAA to replace this with a (necked) stainless steel pin in order to provide a little more strength and haven't sheared it since. > > I also think that when the servo gets very hot (as above) it's internal voltage regulator starts to shut down (as many are designed to do). Again, there is no way of knowing when this happens until realisation that the AP is not tracking! > > v). The LAA will insist upon the stops on the servo, although these stops are not particularly robust and the set up would be better adjusted so that the stops never have to resist the pilot's stick inputs. > > Otherwise, the Trutrak system and its dynamics work extremely well and can do a much better job than the pilot, especially in turbulent conditions. > > Have you found a setting on your Skymap that allows adjustment of the pre-emptive steering sensitivity (or "turn anticipation")? > > > > Duncan McF. > > On 03 January 2023 at 13:10 David Cripps > wrote: > > > So, I've slowly been making some progress on this, having mocked up the whole system out of the aircraft. I have now been able to test it in the workshop and yesterday in a car (it needed to be moving to get a track signal). See attached photo. However, I now have a couple more questions/observations! > > i) It seems that the Skymap III that I used in these tests works in terms of making the servo move and display a track on the Trutrak, so that's progress! However, I note from the Skymap manual that it only gives its GPS info every 2 seconds, rather than the once every second that the Trutrak recommends to avoid 'wandering'. Peter, in your post you mentioned that you were using a Skymap III - have you ever had a problem with this (assuming your A/P is the Trutrak Digitrak too)? Alan, is the Garmin 196 that you've mentioned as suitable, able to be set to give data at the 'once per second' rates, as from the manual it seems it may too default to once every 2 seconds? > > ii) I noticed when testing in the car, that when the track that was displayed in the Trutrak was close to what we were actually tracking (as read from the Skymap), that the servo was more or less static, and moved in the correct direction when there was a small deviation between what was set on the Trutrak and what we were tracking. However, because our roads are not straight, there were frequently occasions when the actual track from the Skymap was miles away from that set on the Trutrak. In that situation the servo went a bit crazy and rotated its arm by many more degrees than it could ever do in the plane. Is this to be expected in this rather 'offline' mode? I can imagine that when the Trutrak senses that its control input is not creating the sort of aircraft track change that it had expected, that it just moves the servo even further in order to try to get aircraft to do something? > > iii) Clearly my mock-up does not provide any sort of 'force feedback' to the servo control arm (ie the arm is completely free to rotate as it likes). In an aircraft, would this be taken care of by aerodynamic feedback via the aileron torque tube? What happens to the servo when it reaches the full movement that the aileron would allow (the point when the control column hits its roll stops)? > > iv) I can imagine that I wouldn't want the servo ever applying full aileron to create a turn as that would make for a very violent manoeuvre! I see that there are settings that can be adjusted in the Trutrak set-up menus that control activity level and also control maximum torque. What values have people set in theirs? I note that when I have set the recommended value of 12 for the torque, it is almost impossible to override the servo arm when the A/P is engaged (though I appreciate that with no control column attached the leverage I can apply to the servo arm with my fingers is very low. I also appreciate that normally if one wanted to override the A/P you would disengage it first). > > v) Lastly (for now!) has anyone fitted physical 'stops' to the servo body that the servo arm would hit to ensure that the servo can never try to move the pushrod beyond the point where full aileron is applied? > > Apologies for all the questions but I want to make sure it is really working correctly before I contort myself to fit it into the aircraft itself! > > Best regards > > David > > On 19/11/2022, 16:26, "Alan Burrill" > on behalf of alanb@dpy01.co.uk >> wrote: > > >> > > > Ok I=99ve had a. Ha ce to fly mine with the GPS feed off. > > > As Duncan says below the display drops to show -|=94|- but maintains the track last set or you are holding when you switch it on. > > > The are no heading digits on the display so you will need use your compass/DI to show that. > > > If you press the left or right =A4=B5=EF=B8=8F buttons then you can alter the track the AP is following either left or right and a number appears which if you press the button you can increase or decrease after the AP locks on the numbers disappear and you have the -|=94|- on the display. > > > Useful if you have a GPS failure but wouldn=99t want that as normal mode of operation so my suggestion is you need a GPS feed with the right NEMA message set to get the most out of the AP and the ability for it to follow a track you have programmed in is a bonus. > > > One word of caution, I have come across some GPS that don=99t put out any messages, even the position message for driving a Transponder ADS-B output, unless there is a track in the GPS. That was how some of the older version worked, GARMIN 430 and possible the early AVMAP were guilty of that. > > > Hope that helps. > > > Alan > > > Sent from my iPad > > On 10 Nov 2022, at 10:52, D McFadyean >> wrote: > >> > > Digitrak only needs basic positional information from the GPS on a regular basis. It will use this information to fly the track that has been set on the Digitrak. > If a route is programmed in to the GPS, it will fly that too (with different commands being set at the Digitrak control head to enable this), so long as the GPS is also putting out the crosstrack error signal; not all of them do. > > Duncan McF. > > > > > > s.com/Navigator?Europa-List > > ion> > | Rowland Carson ... that's Rowland with a 'w' ... | http://www.rowlandcarson.org.uk | Skype, Twitter: rowland_carson Facebook: Rowland Carson ________________________________ Message 6 _____________________________________ Time: 02:30:13 PM PST US From: Dpc Subject: Re: Europa-List: Trutrak AP with Garmin GPS 18x 5Hz --- MIME Errors - No Plain-Text Section Found --- A message with no text/plain MIME section was received. The entire body of the message was removed. Please resend the email using Plain Text formatting. HOTMAIL is notorious for only including an HTML section in their client's default configuration. If you're using HOTMAIL, please see your email application's settings and switch to a default mail option that uses "Plain Text". --- MIME Errors No Plain-Text Section Found --- ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.