---------------------------------------------------------- RV-List Digest Archive --- Total Messages Posted Sat 12/24/05: 34 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:50 AM - Ews Bull air races (charles heathco) 2. 06:06 AM - Re: Ews Bull air races (luckymacy@comcast.net (lucky)) 3. 06:10 AM - CG issues, was Battery on 200 HP Tubro 7A (Glen Matejcek) 4. 07:01 AM - Re: CG issues, was Battery on 200 HP Tubro 7A (Ken Simmons) 5. 07:06 AM - Kens report on exceeding VNE at Alt. (charles heathco) 6. 07:08 AM - Re: CG issues, was Battery on 200 HP Tubro 7A (Kevin Horton) 7. 07:33 AM - Re: Kens report on exceeding VNE at Alt. (Dan Beadle) 8. 07:51 AM - Greetings (charles heathco) 9. 08:23 AM - Re: Battery on 200 HP Tubro 7A (Jeff Dowling) 10. 08:29 AM - Re: Kens report on exceeding VNE at Alt. (Ron Lee) 11. 09:13 AM - Re: CG issues, was Battery on 200 HP Tubro 7A (Mickey Coggins) 12. 09:20 AM - Re: Battery on 200 HP Tubro 7A () 13. 10:03 AM - Re: Kens report on exceeding VNE at Alt. (Kevin Horton) 14. 10:19 AM - Vortex Generators: one RV4 experience and cruise penalty discussion (Mark Todd) 15. 10:34 AM - Re: Kens report on exceeding VNE at Alt. (Rob Prior (rv7)) 16. 11:36 AM - Re: Kens report on exceeding VNE at Alt. (LessDragProd@aol.com) 17. 11:51 AM - Dynafocal motor mounts (Vincent Osburn) 18. 12:28 PM - Market value of our RVs (was battery location for 200 HP turbo 7A (Stephen J. Soule) 19. 12:29 PM - Market value of our RVs (was battery location for 200 HP turbo 7A (Stephen J. Soule) 20. 01:25 PM - Re: Dynafocal motor mounts (Dick DeCramer) 21. 01:37 PM - Re: Kens report on exceeding VNE at Alt. (Dan Beadle) 22. 01:50 PM - Fittings and sealants (Bob Collins) 23. 02:55 PM - Re: Market value of our RVs (was battery location for 200 HP turbo 7A) (LarryRobertHelming) 24. 02:55 PM - Re: Kens report on exceeding VNE at Alt. (Alex Peterson) 25. 03:12 PM - Re: Fittings and sealants (linn walters) 26. 03:59 PM - Re: Kens report on exceeding VNE at Alt. (Ron Lee) 27. 04:11 PM - Re: Kens report on exceeding VNE at Alt. (rv6n6r@comcast.net) 28. 04:32 PM - Re: Kens report on exceeding VNE at Alt. (Olen Goodwin) 29. 05:06 PM - Time in the tanks, was Kens report on exceeding VNE at Alt. (Michael McGee) 30. 05:38 PM - Re: Kens report on exceeding VNE at Alt. (sportav8r@aol.com) 31. 05:40 PM - Re: Kens report on exceeding VNE at Alt. (Dan Beadle) 32. 06:05 PM - Re: Kens report on exceeding VNE at Alt. (Gordon or Marge Comfort) 33. 06:20 PM - Re: Fittings and sealants (LARRY ADAMSON) 34. 07:53 PM - Re: Time in the tanks (Ed Holyoke) ________________________________ Message 1 _____________________________________ Time: 05:50:59 AM PST US From: "charles heathco" Subject: RV-List: Ews Bull air races --> RV-List message posted by: "charles heathco" Hiya m, wanted to put this out for all who may not know about it, NBC is airing the races at 2pm Central, today, Sat. Charlie heathco Do not archive ________________________________ Message 2 _____________________________________ Time: 06:06:55 AM PST US From: luckymacy@comcast.net (lucky) Subject: Re: RV-List: Ews Bull air races --> RV-List message posted by: luckymacy@comcast.net (lucky) Thanks for the info. TV guide's show description doesn't sound like today's show is dedicated to just the air race so don't get your hopes up too high. Hope I'm wrong. lucky -------------- Original message -------------- From: "charles heathco" > --> RV-List message posted by: "charles heathco" > > Hiya m, wanted to put this out for all who may not know about it, NBC is airing > the races at 2pm Central, today, Sat. Charlie heathco Do not archive > > > > > > Thanks for the info. TV guide's show description doesn't sound like today's show is dedicated to just the air race so don't get your hopes up too high. Hope I'm wrong. lucky -------------- Original message -------------- From: "charles heathco" cheathco@junct.com -- RV-List message posted by: "charles heathco" Hiya m, wanted to put this out for all who may not know about it, NBC is airing the races at 2pm Central, today, Sat. Charlie heathco Do not archive _- - List Contribution Web Site - ________________________________ Message 3 _____________________________________ Time: 06:10:16 AM PST US From: "Glen Matejcek" Subject: RV-List: CG issues, was Battery on 200 HP Tubro 7A --> RV-List message posted by: "Glen Matejcek" >Be careful that you consider the polar moment of inertia problem as well. >Think dumbbells vs bowling balls. Both have the cg in the center, but boy oh > >boy are the spin characteristics different. Excellent reminder, Gary! Along those lines, does anybody know whatever became of the fellows that used a 4" or so dia tube through the outboard LE lightening holes as aux fuel tanks? They were at OSH a couple years ago, trying to sell their idea. At the time they hadn't done any spin testing, and didn't seem to have considered roll coupling or the effects of maneuvering on the location of the fuel within the tanks... Glen Matejcek aerobubba@earthlink.net ________________________________ Message 4 _____________________________________ Time: 07:01:31 AM PST US From: "Ken Simmons" Subject: Re: RV-List: CG issues, was Battery on 200 HP Tubro 7A --> RV-List message posted by: "Ken Simmons" Mabye www.safeair1.com? Ken ---------- Original Message ---------------------------------- From: "Glen Matejcek" >--> RV-List message posted by: "Glen Matejcek" > > >>Be careful that you consider the polar moment of inertia problem as well. >>Think dumbbells vs bowling balls. Both have the cg in the center, but boy >oh >> >>boy are the spin characteristics different. > >Excellent reminder, Gary! Along those lines, does anybody know whatever >became of the fellows that used a 4" or so dia tube through the outboard >LE lightening holes as aux fuel tanks? They were at OSH a couple years >ago, trying to sell their idea. At the time they hadn't done any spin >testing, and didn't seem to have considered roll coupling or the effects of >maneuvering on the location of the fuel within the tanks... > >Glen Matejcek >aerobubba@earthlink.net > > ________________________________ Message 5 _____________________________________ Time: 07:06:56 AM PST US From: "charles heathco" Subject: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: "charles heathco" I found the report of dangers of exeeding VNE at Alt. very sobering. First I new about it. I have unknowingly done it and was thinking about the time I was going downhill from 13500' at redline (realized I was going to overshoot into the Atl class B outer ring) I remember the 296 was showing close to 250mph, and I thought that was a real plus. (6A with 150hp) Lucky for me, air was smooth as glass, and I slowed down when I slipped under the outer ring. Now that I have read Kens report, I wont be doing that again, Charlie Heathco ________________________________ Message 6 _____________________________________ Time: 07:08:12 AM PST US From: Kevin Horton Subject: Re: RV-List: CG issues, was Battery on 200 HP Tubro 7A --> RV-List message posted by: Kevin Horton On 24 Dec 2005, at 09:09, Glen Matejcek wrote: > --> RV-List message posted by: "Glen Matejcek" > > > >> Be careful that you consider the polar moment of inertia problem >> as well. >> Think dumbbells vs bowling balls. Both have the cg in the center, >> but boy > oh >> >> boy are the spin characteristics different. > > Excellent reminder, Gary! Along those lines, does anybody know > whatever > became of the fellows that used a 4" or so dia tube through the > outboard > LE lightening holes as aux fuel tanks? They were at OSH a couple > years > ago, trying to sell their idea. At the time they hadn't done any spin > testing, and didn't seem to have considered roll coupling or the > effects of > maneuvering on the location of the fuel within the tanks... It is instructive to look at how spins are treated in FAR 23 aircraft. There are two possibilities: Spins are prohibited - one-turn spins are done in every configuration (i.e. all combinations of flap, landing gear, CG, etc). This covers off the case of an inadvertent stall, followed by incipient spin with immediate pilot recovery. Spins are approved - a full matrix of six-turn spin tests are done in the configuration(s) that are approved for spins. One-turn spins are done in the other configurations. If aerobatics are approved, then the full range of spin tests must be done, as there is a very real risk of ending up in a spin due to a botched attempt at an aerobatic manoeuvre. I believe the prudent RV owner of an aircraft with mods that might affect the spin characteristics would do one of two things: 1. Do a full range of spin tests to be sure than any issues are found during the flight test program when you are prepared to deal with it. or, 2. Placard the aircraft as "Aerobatics and spins are prohibited". Do a test program of one-turn spins only. Note: It would be quite acceptable to placard "Aerobatics and spins are prohibited with fuel in the outboard tanks", and then only do the six-turn spin tests with those tanks empty. One turn spin tests should be done with fuel in those tanks. Some of the mods that people propose could have an adverse effect on flight characteristics, including spins. This is OK, as long as the builder does a full flight test program to determine whether the handling is acceptable. I get concerned when I read about builders "flying off the test hours" as if there was no need to do much flight testing, and all they had to do was log 25 or 40 hours so they could close off the Phase 1 test program. If there are handling or performance problems, the test phase is the time to find them. Then you can either modify the aircraft to fix the problems, or determine a reduced flight or weight/CG envelope to avoid the problems, or develop operational techniques/limitations to avoid the problem areas. It is a lot safer to find the problems when you are testing than it is to have them catch you by surprise later. Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://www.kilohotel.com/rv8 ________________________________ Message 7 _____________________________________ Time: 07:33:30 AM PST US Subject: RE: RV-List: Kens report on exceeding VNE at Alt. From: "Dan Beadle" --> RV-List message posted by: "Dan Beadle" I am still troubled by the Vne argument. For years, I have talked about density of the air mass - it is molecules that affect the airplane, not speed. At an altitude, more speed = more molecules. That would argue to IAS, not TAS for the Vne limit. An article this month in flying seems to support this thought. They talk about the Vne on Columbia. They set it based at 260K. Flying discusses why the decreasing Vne doesn't make sense at these sub-sonic speeds, but is an artifact of setting Vne at or above the magic number of 260K. Finally, the FAA chart, referenced in the article and shown in FAR 23, shows IAS as the limiting factor, NOT TAS. (Seems like it should be CAS, not IAS, but that is another argument). I don't want the tail falling off, but I also don't want to artificially limit the performance of the airframe. There are a lot of issues on adding horsepower - cg shifts, more weight on the firewall (50# x 9G limit - 450# more on motor mounts/firewall), etc. Can anyone site any definitive references that would add more light on the IAS/TAS issue for Vne. I am not sure Van's is right here. Thanks Dan Beadle -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of charles heathco Subject: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: "charles heathco" I found the report of dangers of exeeding VNE at Alt. very sobering. First I new about it. I have unknowingly done it and was thinking about the time I was going downhill from 13500' at redline (realized I was going to overshoot into the Atl class B outer ring) I remember the 296 was showing close to 250mph, and I thought that was a real plus. (6A with 150hp) Lucky for me, air was smooth as glass, and I slowed down when I slipped under the outer ring. Now that I have read Kens report, I wont be doing that again, Charlie Heathco ________________________________ Message 8 _____________________________________ Time: 07:51:47 AM PST US From: "charles heathco" Subject: RV-List: Greetings --> RV-List message posted by: "charles heathco" Wanted to say thanks to all the folks on this list who have shared helpfull info with me this year, and am happy to say that all my problems have happened in a good way, (catastrofic mag failure happened on the ground, Trailer tires blew out durring move 1/4 mile from I-10 Exit near tire store, and so on.)Merry Christmas to all, Charlie heathco. Do not archive ________________________________ Message 9 _____________________________________ Time: 08:23:49 AM PST US From: "Jeff Dowling" Subject: Re: RV-List: Battery on 200 HP Tubro 7A --> RV-List message posted by: "Jeff Dowling" Well, it is EXPERIMENTAL. Shemp/Jeff Dowling RV-6A, N915JD 235 hours Chicago/Louisville ----- Original Message ----- From: Subject: Re: RV-List: Battery on 200 HP Tubro 7A > --> RV-List message posted by: UFOBUCK@aol.com > > I think you should put the battery anywhere you want. > You've not followed Van's recommendations relative to the powerplant and > you > damn sure shouldn't call it a RV-7A. > I would hope the other RV-7 builders feel the same way. When the airplane > bites you in the butt I don't think that they should get painted with the > same > brush of building and flying an unsound airplane. > By the way I said "when" it bites you, not" if"'. > > BClary > RV-6A finished, flown and sold > > > ________________________________ Message 10 ____________________________________ Time: 08:29:20 AM PST US From: Ron Lee Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: Ron Lee At 08:06 AM 12/24/2005, you wrote: >--> RV-List message posted by: "charles heathco" > >I found the report of dangers of exeeding VNE at Alt. very sobering. First >I new about it. I have unknowingly done it and was thinking about the time >I was going downhill from 13500' at redline (realized I was going to >overshoot into the Atl class B outer ring) I remember the 296 was showing >close to 250mph, and I thought that was a real plus. (6A with 150hp) Lucky >for me, air was smooth as glass, and I slowed down when I slipped under >the outer ring. Now that I have read Kens report, I wont be doing that >again, Charlie Heathco Note that GPS gives you GROUNDSPEED so with a significant tailwind your airspeed would be mucho lower. Ron Lee ________________________________ Message 11 ____________________________________ Time: 09:13:23 AM PST US From: Mickey Coggins Subject: Re: RV-List: CG issues, was Battery on 200 HP Tubro 7A --> RV-List message posted by: Mickey Coggins Kevin Horton wrote: > I get concerned when I read about builders "flying off the test > hours" as if there was no need to do much flight testing, and all > they had to do was log 25 or 40 hours so they could close off the > Phase 1 test program. If there are handling or performance problems, > the test phase is the time to find them. Then you can either modify > the aircraft to fix the problems, or determine a reduced flight or > weight/CG envelope to avoid the problems, or develop operational > techniques/limitations to avoid the problem areas. It is a lot safer > to find the problems when you are testing than it is to have them > catch you by surprise later. Kevin, I agree completely. I'm looking forward to the results of your Phase 1 testing, and "copying" all your test cards. Your AFM is really outstanding, and has saved me a lot of time. -- Mickey Coggins http://www.rv8.ch/ #82007 finishing do not archive ________________________________ Message 12 ____________________________________ Time: 09:20:32 AM PST US From: Subject: RV-List: Re: Battery on 200 HP Tubro 7A --> RV-List message posted by: Aubrey: ALTITUDE: First I think the call to NOT call your plane a RV is overkill in my opinion. I like to let the facts speak for themselves. The Turbo only makes more HP at high altitudes, and yes you must observe speed limitations. This is not rocket science or a real big issue, but the pilot needs to understand the effect of more power will have at higher altitudes. RV's can, have and do fly in the FL200's anyway, And yes if you are at FL180 you need to observe that your TAS does not exceed your sea level (IAS) Vne limit Van specifies (or about 170 mph IAS). This is conservative, but of course progressive flight test should be done. WEIGHT: As far as weight 40 lbs for the turbo can be offset but a lighter prop and YES moving the battery aft. You can always use a light composite oil pan, put the Strobe pack in the back and so on. W&B will NOT be an issue. However your gross weight will be higher and thus you may be limited to solo aerobatics (I don't know that but easy enough to check) and you will no doubt have less payload capacity (if you keep the stock 1800 lb gross). Really there are 6 cylinder RV-7/-8's out there. A turbo is a bolt on engine add on. Many a STC has been issued for aftermarket turbos on factory planes. There are plenty single engine factory planes that come in both normally aspirated and turbo versions, planes like C210T, Mooney's and Bonanza's. The airframes are virtually the same. I usually say build it per plans, but I think the call to denounce your plane as NOT RV-7/A is over kill. Yes 40 lbs is a lot of weight, but the aircraft was designed around a heavy IO360 (200HP) engine. You might as well say everyone who puts a Mazda, Subaru engine or modifies their Lycoming engine or uses a clone Lycoming engine in their RV is not a RV. TURBO FOR ME? NO, However if yes for you, you need to be aware of your TAS at altitudes. My opinion is turbo charges are not a panicia for everything, there are lots draw backs I am very aware of. The fact you need to suck O2 and file IFR to take advantage the TURBO, limits it's use. Also without a inter-cooler you are looking at decreasing efficiency and TEMP limits, which will become you new limitation, engine temperature. Even with an inter-cooler turbo piston engines are not a slam dunk. If you want more high altitude power building a slightly pumped up engine (high compression pistons, EI) will give you better altitude performance. Keeping the wight down also helps. As it is now, solo you can cruise right up near FL180 with out a turbo. BATTERY: Here is a list of CG/Empty weights of RV-7's at Dan's web site http://www.rvproject.com/wab/ Using this info and doing some W&B you can play around with the effect of the extra weight has and what effect the batterie'(s) will have moving it (them) aft. You only have really two practical choices of locations: Firewall (under cowl or cabin side) or behind the baggage compartment. The other choice is to use a heavy battery or light battery. My first choice would be stick with plans, but with all the turbo stuff putting the battery on the cooler cabin side of the firewall will give more room for the STUFF (inter cooler, large large oil cooler, lots of hoses and ducts). Aft baggage is a pain and will add overall weight and long battery cables, but it is doable. HERE IS A PICTURE OF TURBO RV-8 http://img69.imageshack.us/img69/4687/image439ccea15c0c11d96hp. jpg If you want a turbo plan on very crowded cowl. This is a view of the oil cooler (notice how big!). The inter-cooler is on the other side which also gets air from a NACA scoop on the side of the cowl. Maintenance will be more frequent and it will require more pilot attention and skill to operate properly. As far as insurance that is between you and the insurer. I know they will want a IFR rated pilot and more time. When I was a CFI/II/MEI the members of the club needed way more time to fly the turbo aircraft models we had (Mooney/T210). Why? More pilots got into Weather problems in a higher flying fast plane, thus the IFR rating was required. Bottom line is if you are able to take on a Turbo project you can do some simple W&B exercices and figure where your battery ballast needs to be. Good Luck George Match: #15 Message: #134873 From: "Aubrey" Subject: Battery on 200 HP Tubro 7A Date: Dec 22, 2005 I am building an RV7a with a IO 360 / 200 HP with Turbo Charger. The engine is 40 pounds heavier plus the turbo. Should the battery be moved aft because of the added weight. Aubrey Price N600AP --------------------------------- ________________________________ Message 13 ____________________________________ Time: 10:03:19 AM PST US From: Kevin Horton Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: Kevin Horton On 24 Dec 2005, at 10:32, Dan Beadle wrote: > --> RV-List message posted by: "Dan Beadle" > > > I am still troubled by the Vne argument. For years, I have talked > about > density of the air mass - it is molecules that affect the airplane, > not > speed. At an altitude, more speed = more molecules. That would > argue to > IAS, not TAS for the Vne limit. > > An article this month in flying seems to support this thought. They > talk > about the Vne on Columbia. They set it based at 260K. Flying > discusses > why the decreasing Vne doesn't make sense at these sub-sonic > speeds, but > is an artifact of setting Vne at or above the magic number of 260K. > > Finally, the FAA chart, referenced in the article and shown in FAR 23, > shows IAS as the limiting factor, NOT TAS. (Seems like it should be > CAS, > not IAS, but that is another argument). > > I don't want the tail falling off, but I also don't want to > artificially > limit the performance of the airframe. There are a lot of issues on > adding horsepower - cg shifts, more weight on the firewall (50# x 9G > limit - 450# more on motor mounts/firewall), etc. > > Can anyone site any definitive references that would add more light on > the IAS/TAS issue for Vne. I am not sure Van's is right here. Van's pronouncements on VNE have me baffled as well. From a practical point of view, there are many factors that the designer and builder should consider when setting VNE. Design issues: Gust loads - air is not always smooth. For a given strength of turbulence, the loads on the structure increase as the airspeed increases. FAR 23 covers this by requiring that the structure be strong enough to sustain a 25 ft/sec vertical gust when the aircraft is flying at VNE. The assumed gusts have a very specific size and shape. The higher the TAS the less time is required to penetrate the gust, so the loads build faster. The higher the EAS, the higher the loads. The result is that the gust loads increase with both EAS and TAS. Windscreen loads - the loads on the windscreen increase as the airspeed increases. If the windscreen is flimsy enough, this may limit VNE. This is probably not an issue with RVs, unless the builder wants to increase VNE to a very large value. Windscreen loads increase with EAS, which is close enough to CAS for speeds less than 250 kt and altitudes lower than 10,000 ft. Wing loads - divergence - if something causes the wing to twist nose up slightly, the increased angle of attack causes the wing to create more lift, which could cause it to twist nose up some more. If the speed is high enough, this can cause a vicious cycle that leads to wing failure. This is called divergence. This may limit VNE on some aircraft. Wing divergence loads go up with EAS. Bird strike - some aircraft have VNE reduced to ensure that collision with a certain sized bird won't cause wing or tail structural failure. Flutter - if you fly fast enough, you enter a region where flutter may occur. There are many different types of flutter, and each type has its own relationship to EAS or TAS. The latest information from Van's seems to suggest that for his designs, he considers TAS as the critical factor. Flight test issues (i.e. something for the builder to determine): It is possible that the aircraft handling qualities may deteriorate as the speed increases. The stick force per g may become dangerously low (this is a general statement, not aimed at RVs). It may be necessary to reduce VNE to ensure that the handling is acceptable inside the approved flight envelope. Note - I am not a structural engineer. There are probably other aspects that I have left out, and my description of the above aspects is incomplete. For a type certificated aircraft, the manufacturer is required to specify VNE such that there are no structural, handling, etc problems inside the approved flight envelope. For lower performance aircraft, it is common to see VNE express as IAS, and that value is good no matter the altitude. For higher performance aircraft, VNE (in IAS) may decrease as the altitude increases. I looked at the wording about VNE in my RV-8 builder's manual. There isn't much there. VNE is mentioned as a marking to put on the airspeed indicator, but there is no mention that VNE (in IAS) should be reduced as the altitude is increased. It is perfectly reasonable for a builder to interpret the information in the builder's manual as suggesting that the recommended VNE in IAS is acceptable at all altitudes. What should we use as VNE for our RVs? Well, we don't have access to all the information needed to answer that question. Only Van's has the information on the structural design, and flutter, etc. Van should provide some clear guidance. He shouldn't expect each builder to do his own flutter ground and flight test program to determine how VNE should vary with altitude. It may be necessary for him to specify that the VNE in IAS is constant up to XXX ft altitude, then it decreases by Y kt per thousand feet increase in altitude. I'll be sending an e-mail to Van's on this subject. Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://www.kilohotel.com/rv8 ________________________________ Message 14 ____________________________________ Time: 10:19:49 AM PST US From: "Mark Todd" Subject: RV-List: Vortex Generators: one RV4 experience and cruise penalty discussion --> RV-List message posted by: "Mark Todd" I posted VG data for my RV4 several years ago on this list but I don't see it in the archives, so I'll summarize it briefly. Testing was done with temporarily installed VG's so I accumulated before and after data times two as carefully as I knew how as an amateur test pilot without special instrumentation. Bottom line is VG's placed at 10% of chord took 12% off the 1G stall TAS. For those who do competition Sportsman acro in their RV's, VG's make for some very nice differences, especially competition spins. As already mentioned in this thread, dogfighting is significantly different. When you have a 20% smaller turning radius than your opponent, it is a pretty dissimilar fight. Assuming pilots with equal skills and thrust/weight, the fight is usually over in two turns or so. I'd encourage some consideration on the issue of cruise speed loss. By cleaning up intersection drag at the wing root, some planes might actually end up with less total drag at cruise when VG's are in place, even though the VG's have got to be adding parasitic drag. I've heard that it is not uncommon in some light twins with VG's to be faster in cruise. I know I couldn't measure a significant difference at 160 kt TAS cruise in my RV4 with my 10% of chord VG placement. In fact, my raw data from flying many GPS wind triangles showed an average 0.5 kt increase with VG's. One pilot, one airplane. Certainly not statistically significant. As they say, your experience may vary. Please remember that if you're trying to minimize drag penalties at cruise airspeeds, you need to place the VG's at the point where the airflow normally converts to turbulent from laminar at that cruise airspeed. Such a VG placement is not going to maximize slow flight effects. I wonder if some of the differing experiences out there with VG's has to do with where the VG's are placed along the chord line. One might expect a difference between, say, placement at 8 versus 10 percent of chord! Parasitic drag is parasitic drag and the faster you go or the further forward you place the VG's, the more you're going to hurt the top end speed. My data doesn't conflict with those who have measured reductions in cruise speeds as long as they're cruising faster than my 160kt TAS or have their VG placement at less than 10% of chord. Mark RV-4 KAWO "Time: 08:27:09 AM PST US From: Subject: RV-List: Re: Vortex Generators --> RV-List message posted by: Yes it is hard to get accurate data. People who sell them will tell you all kind of things but here is where the NO FREE LUNCH rule comes in. You can expect about 3kts lower stall and about 3 kts lower, less top speed: ________________________________ Message 15 ____________________________________ Time: 10:34:31 AM PST US From: "Rob Prior (rv7)" Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: "Rob Prior (rv7)" On 10:02:40 2005-12-24 Kevin Horton wrote: > It is perfectly reasonable > for a builder to interpret the information in the builder's manual as > suggesting that the recommended VNE in IAS is acceptable at all > altitudes. And this would be correct for any FAR23 certified aircraft. Your airframe doesn't know how high it is, or what the air density is. It doesn't care. It only knows what it thinks the airspeed is, and that number comes from your indicated airspeed. True airspeed is only useful for pilots, so they can plan their next fuel stop. It has nothing to do with the structural capabilities of the aircraft. -Rob (I didn't stay at a holiday inn express last night, but I am an aeronautical engineer...) ________________________________ Message 16 ____________________________________ Time: 11:36:48 AM PST US From: LessDragProd@aol.com Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: LessDragProd@aol.com Better review your text books regarding flutter speed. It is related to TAS, since air density influences airframe structural dampening. Regardless of Ken's RVator article, Vne is an INDICATED airspeed. The structural flutter speed is stated as a TRUE airspeed. IMHO, Ken's article was trying to point out the two airspeeds cross over at some altitude. However, they went to great extremes to NOT provide a flutter speed. (Sometimes it's important to notice what wasn't written.) Regards, Jim Ayers PS In the old days :-), RV-3's were flutter tested at 10% over Vne (Vne=210 mph ias) at around 10,000'. When you are going to sit in the seat, there is a tendency to study the text a little closer. In a message dated 12/24/2005 10:35:27 AM Pacific Standard Time, rv7@b4.ca writes: --> RV-List message posted by: "Rob Prior (rv7)" On 10:02:40 2005-12-24 Kevin Horton wrote: > It is perfectly reasonable > for a builder to interpret the information in the builder's manual as > suggesting that the recommended VNE in IAS is acceptable at all > altitudes. And this would be correct for any FAR23 certified aircraft. Your airframe doesn't know how high it is, or what the air density is. It doesn't care. It only knows what it thinks the airspeed is, and that number comes from your indicated airspeed. True airspeed is only useful for pilots, so they can plan their next fuel stop. It has nothing to do with the structural capabilities of the aircraft. -Rob (I didn't stay at a holiday inn express last night, but I am an aeronautical engineer...) ________________________________ Message 17 ____________________________________ Time: 11:51:38 AM PST US From: "Vincent Osburn" Subject: RV-List: Dynafocal motor mounts --> RV-List message posted by: "Vincent Osburn" Has anybody worn out their dynafocal motor mounts? I think mine are shot or nearly so as I have begun to detect a buzzing vibration heretofore undetected. Very light but reminds me of a dune buggy with solid motor mounts but still very light. Under hood inspection seem OK except the mounts look stretched toward that way in which you might expect them to stretch. Airplane flying since 92 with 900 TT. I didn't own it at the time but I think I remember the builder/ owner/ friend saying something about swapping them around once? What was the bestest cheapest mount to replace them with. Any suggestions or input appreciated. Vince ________________________________ Message 18 ____________________________________ Time: 12:28:54 PM PST US From: "Stephen J. Soule" ) Subject: RV-List: Market value of our RVs (was battery location for 200 HP turbo 7A ) --> RV-List message posted by: "Stephen J. Soule" Listers, This development reminds me ... I often wonder where we can find a good measure of the market value of our RVs. Every year I face this question when I renew my insurance for my flying RV-6A. Any advice out there? Trade-A-Plane shows me asking prices, but where can I find sale prices or insurance settlement information about totaled RVs? Stephen Soule in snowy Vermont RV-6A N227RV PS - I posted this yesterday, but it didn't go through. Forgive me if you've already seen it. -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com ] On Behalf Of RAS Subject: Re: RV-List: Battery on 200 HP Tubro 7A ... you have sold on your RV6A,perhaps at the going market value, therefore making profit, Market value of our RVs (was battery location for 200 HP turbo 7A) Listers, This development reminds me ... I often wonder where we can find a good measure of the market value of our RVs. Every year I face this question when I renew my insurance for my flying RV-6A. Any advice out there? Trade-A-Plane shows me asking prices, but where can I find sale prices or insurance settlement information about totaled RVs? Stephen Soule in snowy Vermont RV-6A N227RV PS - I posted this yesterday, but it didn't go through. Forgive me if you've already seen it. -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of RAS Subject: Re: RV-List: Battery on 200 HP Tubro 7A ... you have sold on your RV6A,perhaps at the going market value, therefore making profit,=20 ________________________________ Message 19 ____________________________________ Time: 12:29:12 PM PST US From: "Stephen J. Soule" ) Subject: RV-List: Market value of our RVs (was battery location for 200 HP turbo 7A ) --> RV-List message posted by: "Stephen J. Soule" Listers, This development reminds me ... I often wonder where we can find a good measure of the market value of our RVs. Every year I face this question when I renew my insurance for my flying RV-6A. Any advice out there? Trade-A-Plane shows me asking prices, but where can I find sale prices or insurance settlement information about totaled RVs? Stephen Soule in snowy Vermont RV-6A N227RV PS - I posted this yesterday, but it didn't go through. Forgive me if you've already seen it. -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com ] On Behalf Of RAS Subject: Re: RV-List: Battery on 200 HP Tubro 7A ... you have sold on your RV6A,perhaps at the going market value, therefore making profit, Market value of our RVs (was battery location for 200 HP turbo 7A) Listers, This development reminds me ... I often wonder where we can find a good measure of the market value of our RVs. Every year I face this question when I renew my insurance for my flying RV-6A. Any advice out there? Trade-A-Plane shows me asking prices, but where can I find sale prices or insurance settlement information about totaled RVs? Stephen Soule in snowy Vermont RV-6A N227RV PS - I posted this yesterday, but it didn't go through. Forgive me if you've already seen it. -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of RAS Subject: Re: RV-List: Battery on 200 HP Tubro 7A ... you have sold on your RV6A,perhaps at the going market value, therefore making profit,=20 ________________________________ Message 20 ____________________________________ Time: 01:25:02 PM PST US From: "Dick DeCramer" Subject: RE: RV-List: Dynafocal motor mounts --> RV-List message posted by: "Dick DeCramer" Vince... Just bought a set from Vans....$55 for each motor mount plus $28.50 for bolt kit. Total was $248.50 plus shipping. They are usually replaced at engine major & in this case a accident after 1400 hours and a mild prop strike but still a prop strike none the less. > Subject: RV-List: Dynafocal motor mounts > > --> RV-List message posted by: "Vincent Osburn" > > Has anybody worn out their dynafocal motor mounts? I think mine are shot or nearly so as I have begun to detect a buzzing vibration heretofore undetected. Very light but reminds me of a dune buggy with solid motor mounts but still very light. Under hood inspection seem OK except the mounts look stretched toward that way in which you might expect them to stretch. Airplane flying since 92 with 900 TT. I didn't own it at the time but I think I remember the builder/ owner/ friend saying something about swapping them around once? > What was the bestest cheapest mount to replace them with. Any suggestions or input appreciated. > > > Vince > > ________________________________ Message 21 ____________________________________ Time: 01:37:16 PM PST US Subject: RE: RV-List: Kens report on exceeding VNE at Alt. From: "Dan Beadle" --> RV-List message posted by: "Dan Beadle" Kevin, your thoughts seem to jive with mine. But Van's makes a big deal about not over-engining a plane because of the Vne issue. You indicated something about flutter and TAS below. It still seems to me that anything aerodynamic would be IAS related. Do you have a source I could dig into further? I am building an RV8. I live at Lake Tahoe - so altitude is always an issue. I am thinking IO360 + CS. My partner wants a turbo-normalized engine. Maybe 180HP, but all the way up to mid teens. That sounds pretty good to me, other than this Vne issue. I normally fly a pressurized twin in the 20's. It would be nice to have plenty of pep to get up to 15000' or so to cross the Sierras. I don't like messing with O2, so we would use that as just a crossing altitude, then drop back down and off of oxygen. We are a ways from engine selection, but we want to avoid "test pilot" as much as possible. Thanks Dan -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of Kevin Horton Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: Kevin Horton On 24 Dec 2005, at 10:32, Dan Beadle wrote: > --> RV-List message posted by: "Dan Beadle" > > > I am still troubled by the Vne argument. For years, I have talked > about > density of the air mass - it is molecules that affect the airplane, > not > speed. At an altitude, more speed = more molecules. That would > argue to > IAS, not TAS for the Vne limit. > > An article this month in flying seems to support this thought. They > talk > about the Vne on Columbia. They set it based at 260K. Flying > discusses > why the decreasing Vne doesn't make sense at these sub-sonic > speeds, but > is an artifact of setting Vne at or above the magic number of 260K. > > Finally, the FAA chart, referenced in the article and shown in FAR 23, > shows IAS as the limiting factor, NOT TAS. (Seems like it should be > CAS, > not IAS, but that is another argument). > > I don't want the tail falling off, but I also don't want to > artificially > limit the performance of the airframe. There are a lot of issues on > adding horsepower - cg shifts, more weight on the firewall (50# x 9G > limit - 450# more on motor mounts/firewall), etc. > > Can anyone site any definitive references that would add more light on > the IAS/TAS issue for Vne. I am not sure Van's is right here. Van's pronouncements on VNE have me baffled as well. From a practical point of view, there are many factors that the designer and builder should consider when setting VNE. Design issues: Gust loads - air is not always smooth. For a given strength of turbulence, the loads on the structure increase as the airspeed increases. FAR 23 covers this by requiring that the structure be strong enough to sustain a 25 ft/sec vertical gust when the aircraft is flying at VNE. The assumed gusts have a very specific size and shape. The higher the TAS the less time is required to penetrate the gust, so the loads build faster. The higher the EAS, the higher the loads. The result is that the gust loads increase with both EAS and TAS. Windscreen loads - the loads on the windscreen increase as the airspeed increases. If the windscreen is flimsy enough, this may limit VNE. This is probably not an issue with RVs, unless the builder wants to increase VNE to a very large value. Windscreen loads increase with EAS, which is close enough to CAS for speeds less than 250 kt and altitudes lower than 10,000 ft. Wing loads - divergence - if something causes the wing to twist nose up slightly, the increased angle of attack causes the wing to create more lift, which could cause it to twist nose up some more. If the speed is high enough, this can cause a vicious cycle that leads to wing failure. This is called divergence. This may limit VNE on some aircraft. Wing divergence loads go up with EAS. Bird strike - some aircraft have VNE reduced to ensure that collision with a certain sized bird won't cause wing or tail structural failure. Flutter - if you fly fast enough, you enter a region where flutter may occur. There are many different types of flutter, and each type has its own relationship to EAS or TAS. The latest information from Van's seems to suggest that for his designs, he considers TAS as the critical factor. Flight test issues (i.e. something for the builder to determine): It is possible that the aircraft handling qualities may deteriorate as the speed increases. The stick force per g may become dangerously low (this is a general statement, not aimed at RVs). It may be necessary to reduce VNE to ensure that the handling is acceptable inside the approved flight envelope. Note - I am not a structural engineer. There are probably other aspects that I have left out, and my description of the above aspects is incomplete. For a type certificated aircraft, the manufacturer is required to specify VNE such that there are no structural, handling, etc problems inside the approved flight envelope. For lower performance aircraft, it is common to see VNE express as IAS, and that value is good no matter the altitude. For higher performance aircraft, VNE (in IAS) may decrease as the altitude increases. I looked at the wording about VNE in my RV-8 builder's manual. There isn't much there. VNE is mentioned as a marking to put on the airspeed indicator, but there is no mention that VNE (in IAS) should be reduced as the altitude is increased. It is perfectly reasonable for a builder to interpret the information in the builder's manual as suggesting that the recommended VNE in IAS is acceptable at all altitudes. What should we use as VNE for our RVs? Well, we don't have access to all the information needed to answer that question. Only Van's has the information on the structural design, and flutter, etc. Van should provide some clear guidance. He shouldn't expect each builder to do his own flutter ground and flight test program to determine how VNE should vary with altitude. It may be necessary for him to specify that the VNE in IAS is constant up to XXX ft altitude, then it decreases by Y kt per thousand feet increase in altitude. I'll be sending an e-mail to Van's on this subject. Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://www.kilohotel.com/rv8 ________________________________ Message 22 ____________________________________ Time: 01:50:07 PM PST US From: "Bob Collins" Subject: RV-List: Fittings and sealants --> RV-List message posted by: "Bob Collins" I just want to double-check something on the use of sealant on various plumbing fittings. This pertains to the admonishment not to use any sealant on flared fittings. Am I correct that you're not talking about use the use of sealant on the flare itself (I certainly get that), but you're saying you don't use sealant on any of the threads to which the nut that holds the flare into the fitting threads? In other words, using the fuel valve as an example: you would use EZ Turn on the threads of the fitting that screw into the valve assembly, but you do not use any sealant on the threads at the other end of that fitting, where the nut that holds the fuel line to the fuel valve threads? Thanks for your patience and insight. Bob St. Paul ________________________________ Message 23 ____________________________________ Time: 02:55:41 PM PST US From: "LarryRobertHelming" Subject: Re: RV-List: Market value of our RVs (was battery location for 200 HP turbo 7A) --> RV-List message posted by: "LarryRobertHelming" Think about it. The value of one plane to another will more than double in value by the instruments installed. Your question is not that easily answered. Your value could be actually what some one would buy it from you for. Your insurance value is probably some thing you would want as a minimum in the event it was totaled out by the insurace company which is probably less than the first. .. Indiana Larry, RV7 Tip Up SunSeeker 77 hours "Please use the information and opinions I express with responsibility, and at your own risk." Achieving a certain level of success in life is only important if you can finally enjoy the level you've reached after you've reached it. L R Helming, who thought of it last. ----- Original Message ----- From: "Stephen J. Soule" Subject: RV-List: Market value of our RVs (was battery location for 200 HP turbo 7A) > --> RV-List message posted by: "Stephen J. Soule" > > Listers, > > This development reminds me ... I often wonder where we can find a good > measure of the market value of our RVs. Every year I face this question > when > I renew my insurance for my flying RV-6A. Any advice out there? > Trade-A-Plane shows me asking prices, but where can I find sale prices or > insurance settlement information about totaled RVs? > > Stephen Soule in snowy Vermont > RV-6A N227RV > > PS - I posted this yesterday, but it didn't go through. Forgive me if > you've > already seen it. > > -----Original Message----- > From: owner-rv-list-server@matronics.com > [mailto:owner-rv-list-server@matronics.com > ] On Behalf Of RAS > Sent: Friday, December 23, 2005 6:59 AM > To: rv-list@matronics.com > Subject: Re: RV-List: Battery on 200 HP Tubro 7A > > ... you have sold on your RV6A,perhaps at > the going market value, therefore making profit, > > > > > 5.5.2657.73"> > Market value of our RVs (was battery location for 200 HP turbo 7A) > > > Listers, > > > This development reminds me ... I often wonder where we can find a good > measure of the market value of our RVs. Every year I face this question > when I renew my insurance for my flying RV-6A. Any advice out there? > Trade-A-Plane shows me asking prices, but where can I find sale prices or > insurance settlement information about totaled RVs? > > > Stephen Soule in snowy Vermont > > RV-6A N227RV > > > PS - I posted this yesterday, but it didn't go through. Forgive me if > you've already seen it. > > > -----Original Message----- > > From: owner-rv-list-server@matronics.com > [mailto:owner-rv-list-server@matronics.com] On Behalf Of RAS > > Sent: Friday, December 23, 2005 6:59 AM > > To: rv-list@matronics.com > > Subject: Re: RV-List: Battery on 200 HP Tubro 7A > > > ... you have sold on your RV6A,perhaps at > > the going market value, therefore making profit, > > > ________________________________ Message 24 ____________________________________ Time: 02:55:42 PM PST US From: "Alex Peterson" Subject: RE: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: "Alex Peterson" > > And this would be correct for any FAR23 certified aircraft. > Your airframe doesn't know how high it is, or what the air > density is. It doesn't care. > It only knows what it thinks the airspeed is, and that number > comes from your indicated airspeed. > > True airspeed is only useful for pilots, so they can plan > their next fuel stop. It has nothing to do with the > structural capabilities of the aircraft. > > -Rob > (I didn't stay at a holiday inn express last night, but I am > an aeronautical engineer...) I must respectfully disagree with some of what you wrote. The airframe does indeed care about TAS, in two significant ways. One is dealing with compressibility, which obviously doesn't apply to RV's. The other has to do with what Ken wrote about. Flutter is a condition when some natural frequency of a structure is excited by some external forces which happen to be of the same frequency (this is a little simplified, but the idea is the same). For example, say that some turbulence causes the horizontal stabilizer to deflect upward by a small amount (this could be miniscule). The amount of time which will pass between this event and when the same air disturbance passes the elevator is inversely related to the TAS, not IAS. If this period of time happens to be resonant with the natural frequency of the horizontal stabilizer and elevator, it could begin being self exciting, with ever increasing amplitude. The structure does not care how low the IAS speed is, only what the TAS is. I suspect that there is some mitigation of flutter risk as IAS drops due to lowering external forces, but what Ken wrote makes complete sense. Watching a slow motion video of HS/elevator flutter is quite alarming, and most end with structural failure. Alex Peterson RV6-A N66AP 702 hours Maple Grove, MN ________________________________ Message 25 ____________________________________ Time: 03:12:55 PM PST US From: linn walters Subject: Re: RV-List: Fittings and sealants --> RV-List message posted by: linn walters Bob Collins wrote: >--> RV-List message posted by: "Bob Collins" > >I just want to double-check something on the use of sealant on various >plumbing fittings. This pertains to the admonishment not to use any sealant >on flared fittings. Am I correct that you're not talking about use the use >of sealant on the flare itself (I certainly get that), but you're saying you >don't use sealant on any of the threads to which the nut that holds the >flare into the fitting threads? > True. >In other words, using the fuel valve as an example: you would use EZ Turn on >the threads of the fitting that screw into the valve assembly, but you do >not use any sealant on the threads at the other end of that fitting, where >the nut that holds the fuel line to the fuel valve threads? > Not familiar with EZ turn, but if you're really bent on using a sealant on fittings, only use it on tapered fittings, and leave 1 or two threads on the end clean. That goes for both teflon tape, and teflon paste. Aluminum fittings will seal much better than steel ones ...... or where at least one surface is aluminum ...... probably due to the softness of the aluminum Vs. the steel. I don't use any sealant at all unless I have a leak to fix. Linn Do not archive > >Thanks for your patience and insight. > >Bob >St. Paul > > > > > > > > > -- ________________________________ Message 26 ____________________________________ Time: 03:59:56 PM PST US From: Ron Lee Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: Ron Lee >True airspeed is only useful for pilots, so they can plan their next fuel >stop. Some might question my piloting abilities but I don't worry much about TAS. I use groundspeed for fuel stop considerations (using GPS). Ron Lee Do not archive ________________________________ Message 27 ____________________________________ Time: 04:11:50 PM PST US From: rv6n6r@comcast.net Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: rv6n6r@comcast.net Just curious... how many RV accidents have there been that have been attributed to flutter? Seems like it'd be one of those things that could be detected in a post-crash investigation. I've never heard of one, and I KNOW some people out there have exceeded VNE before.... could be a testament to the margins built into Van's RVs? Don't remember if Ken mentioned it in his article either so forgive me if this has already been answered. Randall Henderson RV-6 PS. Don't mind me, I'm just adding fuel to the fire... ;-) do not archive ________________________________ Message 28 ____________________________________ Time: 04:32:51 PM PST US From: "Olen Goodwin" Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: "Olen Goodwin" I've been following this thread, but may have missed something. My question is: What is the Vne based on? Flutter or gust loads? As for a turbo subjecting the airplane to higher airspeeds than safe, I'd say that's the pilot rather than the engine. Almost all jet transports can easily exceed Vne/Vmo any time the pilot wants to; the key is discipline. Just operate the airplane within it's limitations, even if it's capable of exceeding them. The extra performance of a turbocharger (or big engine) is useful almost anywhere in the western US or Canada operating off high altitude airports or over high terrain. You just have to have the professionalism to limit your speeds in accordance with the airplane's aerodynamic and structural limits. Do not archive. org ________________________________ Message 29 ____________________________________ Time: 05:06:26 PM PST US From: Michael McGee Subject: RV-List: Time in the tanks, was Kens report on exceeding VNE at Alt. --> RV-List message posted by: Michael McGee At 15:57 2006-01-24, you wrote: >--> RV-List message posted by: Ron Lee > > > >True airspeed is only useful for pilots, so they can plan their next fuel > >stop. > >Some might question my piloting abilities but I don't worry much about >TAS. I use groundspeed for fuel stop considerations (using GPS). > >Ron Lee > >Do not archive Having landed without the convenience of an airport at one time I find the clock is the best gauge of when to get gas. A high power setting and a good head wind on one south bound trip from UAO put me fueling up at SIY instead of RDD as planned (run those through the GPS). When I put the caps on I had loaded all but 1/2 gallon of my useable fuel (no it wasn't my RV-4). That was a BIG difference between planned and actual. Time is in the tanks (scaled for power setting), not miles. Don't get me wrong, I like GPS, that's the only electronic navigation I have. Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR 13B in gestation mode, RD-1C, EC-2 ________________________________ Message 30 ____________________________________ Time: 05:38:25 PM PST US From: sportav8r@aol.com Subject: Re: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: sportav8r@aol.com So do I run out and erase the redline marking from my ASI tomorrow? It only displays IAS and is therefore worthless as an aid to avoiding flutter, no? Not questioning your explanation of flutter, just the wisdom of painting red lines on our ASI dials as required by the FAR's. -Stormy -----Original Message----- From: Alex Peterson Subject: RE: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: "Alex Peterson" > > And this would be correct for any FAR23 certified aircraft. > Your airframe doesn't know how high it is, or what the air > density is. It doesn't care. > It only knows what it thinks the airspeed is, and that number > comes from your indicated airspeed. > > True airspeed is only useful for pilots, so they can plan > their next fuel stop. It has nothing to do with the > structural capabilities of the aircraft. > > -Rob > (I didn't stay at a holiday inn express last night, but I am > an aeronautical engineer...) I must respectfully disagree with some of what you wrote. The airframe does indeed care about TAS, in two significant ways. One is dealing with compressibility, which obviously doesn't apply to RV's. The other has to do with what Ken wrote about. Flutter is a condition when some natural frequency of a structure is excited by some external forces which happen to be of the same frequency (this is a little simplified, but the idea is the same). For example, say that some turbulence causes the horizontal stabilizer to deflect upward by a small amount (this could be miniscule). The amount of time which will pass between this event and when the same air disturbance passes the elevator is inversely related to the TAS, not IAS. If this period of time happens to be resonant with the natural frequency of the horizontal stabilizer and elevator, it could begin being self exciting, with ever increasing amplitude. The structure does not care how low the IAS speed is, only what the TAS is. I suspect that there is some mitigation of flutter risk as IAS drops due to lowering external forces, but what Ken wrote makes complete sense. Watching a slow motion video of HS/elevator flutter is quite alarming, and most end with structural failure. Alex Peterson RV6-A N66AP 702 hours Maple Grove, MN ________________________________ Message 31 ____________________________________ Time: 05:40:29 PM PST US Subject: RE: RV-List: Kens report on exceeding VNE at Alt. From: "Dan Beadle" --> RV-List message posted by: "Dan Beadle" Good explanation. The resonate frequency argument does make sense - and that is based on TAS - not IAS. Thanks -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of Alex Peterson Subject: RE: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: "Alex Peterson" > > And this would be correct for any FAR23 certified aircraft. > Your airframe doesn't know how high it is, or what the air > density is. It doesn't care. > It only knows what it thinks the airspeed is, and that number > comes from your indicated airspeed. > > True airspeed is only useful for pilots, so they can plan > their next fuel stop. It has nothing to do with the > structural capabilities of the aircraft. > > -Rob > (I didn't stay at a holiday inn express last night, but I am > an aeronautical engineer...) I must respectfully disagree with some of what you wrote. The airframe does indeed care about TAS, in two significant ways. One is dealing with compressibility, which obviously doesn't apply to RV's. The other has to do with what Ken wrote about. Flutter is a condition when some natural frequency of a structure is excited by some external forces which happen to be of the same frequency (this is a little simplified, but the idea is the same). For example, say that some turbulence causes the horizontal stabilizer to deflect upward by a small amount (this could be miniscule). The amount of time which will pass between this event and when the same air disturbance passes the elevator is inversely related to the TAS, not IAS. If this period of time happens to be resonant with the natural frequency of the horizontal stabilizer and elevator, it could begin being self exciting, with ever increasing amplitude. The structure does not care how low the IAS speed is, only what the TAS is. I suspect that there is some mitigation of flutter risk as IAS drops due to lowering external forces, but what Ken wrote makes complete sense. Watching a slow motion video of HS/elevator flutter is quite alarming, and most end with structural failure. Alex Peterson RV6-A N66AP 702 hours Maple Grove, MN ________________________________ Message 32 ____________________________________ Time: 06:05:15 PM PST US From: "Gordon or Marge Comfort" Subject: RE: RV-List: Kens report on exceeding VNE at Alt. --> RV-List message posted by: "Gordon or Marge Comfort" -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of Kevin Horton Subject: Re: RV-List: Kens report on exceeding VNE at Alt. What should we use as VNE for our RVs? Well, we don't have access to all the information needed to answer that question. Only Van's has the information on the structural design, and flutter, etc. Van should provide some clear guidance. He shouldn't expect each builder to do his own flutter ground and flight test program to determine how VNE should vary with altitude. It may be necessary for him to specify that the VNE in IAS is constant up to XXX ft altitude, then it decreases by Y kt per thousand feet increase in altitude. I'll be sending an e-mail to Van's on this subject. Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://www.kilohotel.com/rv8 Kevin: Good luck with Van's. My efforts to extract useful information from Ken Krueger have pretty much come to naught. Either he doesn't think we are intelligent enough to understand or is not inclined to trouble himself. With me, at least, he falls back on dogma without further amplification. With regard to flutter, it would be great to have a good explanation of the flutter margins that the various RV's possess. Ken used the -10 to illustrate the principles he espoused but I don't know if the numbers he used were to be taken literally or he was trying to frighten us into compliance. I can grasp the connection between TAS and flutter even if I can't defend it but to me there is still something wrong with the picture. If the RV's presently flying had narrow flutter margins we should be hearing about airframe failures that are not occuring. I know of one RV-4 that hit 270mph indicated in a maneuver that began at the base of a cumulus cloud above surface elevations at 5000' and more. There was minor airframe damage but no flutter. I tested my -4 to 200kt indicated at about 6000' in smooth air and did not excite the controls. More recently I screwed up a maneuver and saw about 205kt at about 4000' in air that was not smooth. No sign of flutter. How would one improve flutter margins? We balance ailerons to 100%. Would heavier leading edge skins all the way to the tips help? Elevators are balanced to 100% Stiffer stabilizer? How stiff? Higher design load factor airframes? I would really like to know. Flight testing for flutter is scary stuff and one must be prepared to try to evacuate a collapsing airframe. I've been told of methods for mitigating the risk but still have not found in myself the courage to seriously try it. Keep us posted, please. Gordon Comfort N363GC ________________________________ Message 33 ____________________________________ Time: 06:20:25 PM PST US From: "LARRY ADAMSON" Subject: Re: RV-List: Fittings and sealants --> RV-List message posted by: "LARRY ADAMSON" ----- Original Message ----- From: Bob Collins Subject: RV-List: Fittings and sealants Since I've been in the HVAC business for 34 years, and too much experience with gas lines and pipe threads, it's a fact that a threaded gas line fitting will leak with just 4 oz. of natural gas pressure, which is the normal pressure of a homes gas line, & no pipe thread sealer is used. I used thread sealer on all of my tapered pipe thread fittings with exception to plastics. Oil lines, as well as brakes. I use a thread sealer that's compatible with about all petroleum products and oxygen, and I would not feel comfortable without it. Flared fittings should just be metal to metal. --> RV-List message posted by: "Bob Collins" I just want to double-check something on the use of sealant on various plumbing fittings. This pertains to the admonishment not to use any sealant on flared fittings. Am I correct that you're not talking about use the use of sealant on the flare itself (I certainly get that), but you're saying you don't use sealant on any of the threads to which the nut that holds the flare into the fitting threads? In other words, using the fuel valve as an example: you would use EZ Turn on the threads of the fitting that screw into the valve assembly, but you do not use any sealant on the threads at the other end of that fitting, where the nut that holds the fuel line to the fuel valve threads? ________________________________ Message 34 ____________________________________ Time: 07:53:24 PM PST US From: "Ed Holyoke" Subject: RE: RV-List: Time in the tanks --> RV-List message posted by: "Ed Holyoke" A clock is good. A fuel totalizer is better. Read out the time to waypoint on the GPS and compare it to the time till empty on the totalizer then subtract 30 or 45 minutes for reserve. I've often used this technique to change destinations when my planned fuel stop was inaccessible due to weather or headwinds and comfortably got maximum possible range out of the gas on board. Always landed with at least 40 minutes of gas left. The time till empty and fuel remaining are accurate no matter what combination of power and mixture settings you've been using. This is particularly handy when you've been forced to descend and divert by weather and you're burning more gallons per hour than you planned for or when winds aloft are different than forecast. A clock is still necessary for keeping track of the tank in which the remaining fuel resides, though. Pax, Ed Holyoke -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of Michael McGee Subject: RV-List: Time in the tanks, was Kens report on exceeding VNE at Alt. --> RV-List message posted by: Michael McGee At 15:57 2006-01-24, you wrote: >--> RV-List message posted by: Ron Lee > > > >True airspeed is only useful for pilots, so they can plan their next fuel > >stop. > >Some might question my piloting abilities but I don't worry much about >TAS. I use groundspeed for fuel stop considerations (using GPS). > >Ron Lee > >Do not archive Having landed without the convenience of an airport at one time I find the clock is the best gauge of when to get gas. A high power setting and a good head wind on one south bound trip from UAO put me fueling up at SIY instead of RDD as planned (run those through the GPS). When I put the caps on I had loaded all but 1/2 gallon of my useable fuel (no it wasn't my RV-4). That was a BIG difference between planned and actual. Time is in the tanks (scaled for power setting), not miles. Don't get me wrong, I like GPS, that's the only electronic navigation I have. Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR 13B in gestation mode, RD-1C, EC-2