I used the term "angle of incidence" when what I really meant to reference was pitch angle, which may or may not be the same as Angle of Attack. AOA is always in reference to the relative wind, which is not necessarily always a horizontal line. The Deck angle or Pitch angle is in reference to a horizontal line, which is the reference I was using. But you are right in that Angle of Incidence was the incorrect term and that at a lower indicated airspeed in level flight the angle of attack would be higher, so my terms were really bass ackwards. -Jeff
> Sent: Tuesday, March 17, 2020 at 6:51 AM > From: "Chris Kinnaman via KRnet" <krnet@list.krnet.org> > To: "Jeff Scott via KRnet" <krnet@list.krnet.org> > Cc: "Chris Kinnaman" <glid...@spinn.net> > Subject: Re: KR> Dan Diehl's comment to Lee > > I think you reversed the usage of the terms, Jeff. Angle of incidence is > built into the airplane and angle of attack is a variable, as you say, > per airspeed & density, that refers to the wing related to the relative > wind. What you describe happens with gliders at high altitudes as well, > with no consideration of power. Due to low air density, to maintain an > indicated airspeed the nose must be higher than at lower altitudes to > increase the wing's angle of attack, to get the appropriate amount of > lift in the thinner air. Flying higher and higher, things become more > and more like slow flight. > > > > On 3/16/2020 9:12 PM, Jeff Scott via KRnet wrote: > > John, your statement is correct. > > > > Cruising at higher altitudes usually creates a situation where you are > > flying at a higher Angle of Incidence. Pilots often times incorrectly > > interpret the higher deck angle as AOA rather than AOI. The higher angle > > of incidence is not created by altitude itself, but is created by the lower > > amount of power available from a normally aspirated engine at a higher > > altitude for a given throttle setting and thus typically leaves you flying > > at a lower indicated airspeed. The lower indicated airspeed creates a > > higher angle of incidence for a given throttle setting at higher altitudes. > > It's a more complicated way of saying that at higher altitudes, the nose > > is usually a bit higher than while flying at lower altitudes. People take > > that basic truth for flying behind normally aspirated engines, then apply > > the wrong term by interpreting it as AOA rather than AOI. > > > > That should make it about as clear as mud. :o) > > > > -Jeff Scott > > Arkansas Ozarks > > > >> Sent: Monday, March 16, 2020 at 9:39 PM > >> From: "John Martindale via KRnet" <krnet@list.krnet.org> > >> To: 'KRnet' <krnet@list.krnet.org> > >> Cc: "John Martindale" <john_martind...@bigpond.com> > >> Subject: Re: KR> Dan Diehl's comment to Lee > >> > >> "cruising at higher altitudes lowers the AofA for a given indicated > >> airspeed". > >> > >> I think the above statement is incorrect. > >> > >> The weight of an aircraft and lift required to support it does not change > >> with altitude. Lift is proportional to airspeed, AoA, density and wing > >> design....the basic lift formula we are taught as students. > >> > >> Therefore for a "given airspeed" and weight and wing design that we cannot > >> alter in flight, as density decreases with altitude, AoA must be increased > >> up until the aircraft ceiling is reached when the AoA reaches the stall > >> angle. > >> > >> It is only if power is increased to increase the given speed that the AoA > >> can be reduced. > >> > >> Pleased to be corrected. > >> > >> John > >> > >> > >> John Martindale > >> Unit 39 > >> 40 Solitary Islands Way > >> Sapphire Beach NSW 2450 > >> Australia > >> > >> m:0403 432179 > >> email:john_martind...@bigpond.com > >> > >> snip > >> > >> Just thinking out loud here . . . but if angle of attack decreases with an > >> increase of indicated airspeed, and also with a decrease in air density . . > >> . cruising at higher altitudes lowers the AofA for a given indicated > >> airspeed, > >> > >> snip. > >> > >> > >> _______________________________________________ > >> Search the KRnet Archives at > >> https://www.mail-archive.com/krnet@list.krnet.org/. > >> Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > >> see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > >> options. > >> To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org > >> > > _______________________________________________ > > Search the KRnet Archives at > > https://www.mail-archive.com/krnet@list.krnet.org/. > > Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > > options. > > To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org > > > > > > > _______________________________________________ > Search the KRnet Archives at > https://www.mail-archive.com/krnet@list.krnet.org/. > Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options. > To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org > _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
