---------------------------------------------------------- RV10-List Digest Archive --- Total Messages Posted Wed 09/02/15: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:39 PM - Re: Re: ADS-B Receivers (Bill Watson) 2. 04:48 PM - Re: ADS-B Receivers (Bob Turner) ________________________________ Message 1 _____________________________________ Time: 01:39:50 PM PST US Subject: Re: RV10-List: Re: ADS-B Receivers From: Bill Watson Here's some more jacket for the flak... I recently experienced a partial pitot blockage while in IMC. It was one of those all too rare moments when I was hand flying the plane. My GRT HX EFISs presented a perfect attitude display. So perfect that I did not notice the airspeed decay that was quite visible on the airspeed tape. With the engine running normally it was easy flying the attitude indication. However when I switched on the Trutrak AP I noticed the "AS" flag as the AP commanded a dive to prevent a stall. I quickly switched it off, recovered, then tried it again with the same result. I finally asked for vectors to the nearest airport which incidentally led me to declare an emergency. The plane was easily flown using pitch and power in IMC and VMC conditions to an uneventful landing (with trucks rolling). It took some effort but I finally cleared out the insect debris clogging my Gretz pitot. The fact that the GRT HX EFIS maintained it's attitude display independent of airspeed made this a non-event. If my attitude indication had caused me to gradually hand fly the plane into a dive or other unusual attitude things would have been a bit tougher to sort out and recover from. This was a particularly perverse partial pitot blockage. Further 'testing' showed that In fact, the blockage occurred only when flying in wet conditions (wet cloud, mist or rain). Apparently the insect debris was absorbent and would swell up instantly with the slightest bit of moisture. Then it would unblock itself after 10 or 20 minutes of dry conditions. This means everything would be fine until wet IMC was encountered. In my particular setup the outcome was never in doubt and I'm glad the NTSB didn't have to try to sort this one out. Bill "happily flying his kitchen sink of a panel" Watson BTW, I'm flying GRT HX, Trutrak AP and Navworx ADSB - It all works great! On 8/31/2015 3:46 PM, Bob Turner wrote: > Okay, now flak jacket on. IMHO the Skyview is only marginally acceptable for actual IMC, because its attitude solution (horizon) requires accurate airspeed data. Dynon recognized the issue, and a software upgrade attempts to flag bad airspeed and revert to gps data. However, there is at least one report of a partial pitot blockage, where the blockage was bad enough to generate incorrect horizon data, but not bad enough to trigger the switch to gps data. > I believe but am not certain that the turn coordinator bars continued to work properly, so a really good pilot could squint and watch those bars while ignoring the horizon. And/or, throw the switch to put the autopilot into stand alone mode and use that. There are options, which is why I said "marginally". But you must be aware of the possibility. > > -------- > Bob Turner > RV-10 QB > > ________________________________ Message 2 _____________________________________ Time: 04:48:46 PM PST US Subject: RV10-List: Re: ADS-B Receivers From: "Bob Turner" Thanks for reminding me that if the indicated airspeed gets too low, the autopilot is NOT an option. I have the Trio but it has the same feature as the TT, it will dive the airplane to prevent flight below indicated stall speed. -------- Bob Turner RV-10 QB Read this topic online here: http://forums.matronics.com/viewtopic.php?p=446706#446706 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rv10-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RV10-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/rv10-list Browse Digests http://www.matronics.com/digest/rv10-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.