I have been following this thread with some interest and would to contribute my two undervalued cents.
First, SIZE does count. Second, a number of years ago, Don Patterson and I were flying our Jerry Mirlk's designed AstroJeff's on a perfect day for high altitude flying. High clouds and some high haze to help visibility. The Jeff's sported an 11.00" root cord and a 12.00' wingspan. Both Jeff's were high enough that all we could see was a cross shape formed by the fuse and wing. The stabs had disappeared. Later after Don and I regained our senses and both got our AstroJeff's down on the ground one of our club members (his name escapes me) drove in to the Gdshs club field in Troy, MI. and told Don and I that he had circled our AstroJeffs at slightly above 5000' with his 1:1 Piper Cherokee. That would put our Jeffs at or above 4400' from us, since our club field was 600' above sea level. That sorta supports Jack Hiner's comments that the stabs on an AstroJeff disappear around 5000'. Three, Size still counts I say. Regards, Dave, I wish I was in Muncie this weekend, Corven. -------------- Original message ---------------------- From: Randall Brust <[EMAIL PROTECTED]> > JAMES EALY wrote:is > > > > The biggest problem with the cheapies is that they are not temperature > > compensated, or VERY poorly so. > > There are 2 types of temperature dependance with respect to electronic > altimeters. > > The first is how temperature change affects the pressure sensor's ability to > convert pressure into voltage. This relationship should be absolutely > constant > no matter what temperature the sensor is at, but in the real world this is > not > the case. The current state of the art solid state sensors, however, do have > built in temperature compensation circuitry and do a pretty good job in > removing > this effect. A large portion of the remaining temperature effect is also > cancelled out since the AGL altitude is computed by measuring absolute > altitude > in the air, measuring absolute altitude at ground level, and subtracting the > two > values. > > The second is how temperature affects the pressure to altitude algorithm that > all pressure based altimeters use to calculate altitude. Altimeters measure > pressure, not altitude, so a model of the atmosphere is used which predicts > how > pressure varies with altiude. This is an ideal model so it obviously cannot > match the real atmosphere at any time and any place on earth. The models are > also based on an ideal sea level air temperature of 59F. So, if you're not > flying at 59F, the model will be off. There are algorithms to compensate for > this temperature effect and that's why our FlightView software allows you to > enter the temperature of the day you were flying. It should be noted that > this > error can be quite large (like 5%-10%) if you are flying on a very hot or > very > cold day. It should also be noted that on hot days, the altimeter will > actually > read low, so if you fly your non-temperature compensated altimeter on a > summer > day and it says you were at 2000ft, you were probably higher. > > I'd also like to relate the following observation. When we were developing > the > RAM altimeters, we were flying them in 1.5m discus launch gliders and taking > them pretty high. The plots showed that we were getting to around 2000ft. > We > initially didn't believe this so we measured out 2000ft at the flying field > and > one of us held up a glider while the other observed it from 2000ft away. It > was > definitely flyable at that distance and looked about right compared to what > we > saw in the air. > > It is also very important to understand how important the conditions are when > flying at altitude. Contrary to what many believe, the worst type of > conditions > is a clear dark blue sky. The best is a clear sky with nice dense cumulus > clouds. If you get a cloud behind your glider, you can see it twice as high > as > you can with blue sky behind it. Just don't fly out from in front of the > cloud > or Poof! it will be gone. :-) > > Randy > Soaring Circuits > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and > "unsubscribe" requests to [EMAIL PROTECTED] Please note that > subscribe and unsubscribe messages must be sent in text only format with MIME > turned off. Email sent from web based email such as Hotmail and AOL are > generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
