Original Posted By: kmordecai001(at)comcast.net
Pietenpol-List: performance numbers and stall speeds vs. a/c weight
Pietenpol-List: performance numbers and stall speeds vs. a/c weight
Original Posted By: "Cuy, Michael D. (GRC-RXD0)[ASRC Aerospace Corporation]"
Subject: Pietenpol-List: performance numbers and stall speeds vs. a/c weightAfter fixing some ignition and timing issues and installing new lower plugs I did some performance numbers last night withthe airplane.Takeoff weight with me and full fuel was 1034 lbs. 80F OAT and climbing at 40-45 mph yielded 500 fpm rate of climb.Power off stall at 29 mph, power on stall didn't even happen when the air speed was well below 30 and I didn't have the gutsto pull it back to make it break.Thinking my conservative climb speed of 55-60 is making my angle of climb (and rate) too anemic. Still learning after 12 yearsof flying it.Not remembering much of anything from ground school and private pilot theory classes, does an airplane's power on stall speedincrease with gross weight ? So say I went up and tried more power on stalls with a 170 lb. passenger given the same conditionsas I flew last night ?I know air density makes a difference in indicated air speed as on colder days I appear to have a faster cruise speed...and maybe I dowith the prop/engine being more efficient in dense air.Also for the record I did a full-throttle, level flight run to see where I would place in a speed dash with Dan Yocum and would come insecond place. Max throttle yielded 2350 rpm and 84 mph.Mike C.________________________________________________________________________________
Subject: Pietenpol-List: performance numbers and stall speeds vs. a/c weightAfter fixing some ignition and timing issues and installing new lower plugs I did some performance numbers last night withthe airplane.Takeoff weight with me and full fuel was 1034 lbs. 80F OAT and climbing at 40-45 mph yielded 500 fpm rate of climb.Power off stall at 29 mph, power on stall didn't even happen when the air speed was well below 30 and I didn't have the gutsto pull it back to make it break.Thinking my conservative climb speed of 55-60 is making my angle of climb (and rate) too anemic. Still learning after 12 yearsof flying it.Not remembering much of anything from ground school and private pilot theory classes, does an airplane's power on stall speedincrease with gross weight ? So say I went up and tried more power on stalls with a 170 lb. passenger given the same conditionsas I flew last night ?I know air density makes a difference in indicated air speed as on colder days I appear to have a faster cruise speed...and maybe I dowith the prop/engine being more efficient in dense air.Also for the record I did a full-throttle, level flight run to see where I would place in a speed dash with Dan Yocum and would come insecond place. Max throttle yielded 2350 rpm and 84 mph.Mike C.________________________________________________________________________________
Pietenpol-List: Re: performance numbers and stall speeds vs. a/c weight
Original Posted By: "Jack Phillips"
So the logic goes like this: Let's say you have two identical aircraft, one weighing900 lbs and one weighing 1000 lbs. The heavier aircraft will need highertotal lift, given steady state conditions, like cruise at 70 mph. Since liftvaries almost directly with angle of attack, the heavier one needs a higherangle of attack (more lift) to stay even. Airfoils stall at a particular and specific angle of attack regardless of grossweight. The air flowing over the top of the airfoil separates and lift goesaway and it doesn't matter what the weight is. As you slow the aircraft down,the angle of attack increases but the heavier aircraft started with a higherangle so it reaches "stall" first. Power-on stall occurs a a slower airspeed because the engine is providing a significantamount of lift due to the nose high attitude so the airfoil sees whatit thinks is a lighter gross weight. If you have enough power, you can't inducea power-on stall. I wonder if I can hang one of Sean Tucker's AEIOU and sometimesY 580's on my Piet. Would certainly solve the tail heavy issue onceand for all. Might have to drink more beer.Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________
So the logic goes like this: Let's say you have two identical aircraft, one weighing900 lbs and one weighing 1000 lbs. The heavier aircraft will need highertotal lift, given steady state conditions, like cruise at 70 mph. Since liftvaries almost directly with angle of attack, the heavier one needs a higherangle of attack (more lift) to stay even. Airfoils stall at a particular and specific angle of attack regardless of grossweight. The air flowing over the top of the airfoil separates and lift goesaway and it doesn't matter what the weight is. As you slow the aircraft down,the angle of attack increases but the heavier aircraft started with a higherangle so it reaches "stall" first. Power-on stall occurs a a slower airspeed because the engine is providing a significantamount of lift due to the nose high attitude so the airfoil sees whatit thinks is a lighter gross weight. If you have enough power, you can't inducea power-on stall. I wonder if I can hang one of Sean Tucker's AEIOU and sometimesY 580's on my Piet. Would certainly solve the tail heavy issue onceand for all. Might have to drink more beer.Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________
RE: Pietenpol-List: performance numbers and stall speeds vs. a/c weight
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Stall speed (either power-on or power-off) occurs at a HIGHER airspeed athigher weight. That's why performance figures for certified aircraft aretypically shown at gross weight. Think about it, if the stall speed wentdown as the weight goes up, you could therorectically add enough weight soit would never stall, and the fatter the pilot the better the shortfieldperformance would be. The stall actually occurs at the critical angle ofattack (which is a function of the airfoil design), regardless of airspeed.That's why you can get into an accelerated stall at high airspeeds (such asentering a snap roll, or pulling out of a steep dive). For this reason, anAOA meter is a better indication of impending stall than an airspeedindicator, but since they tend to be more expensive, we use the airspeed asthe indication.I've always climbed my Piet at 50 - 55 mph, and get between 100 and 500 fpmdepending on loading and density altitude. Maybe tomorrow I'll do some testflying and try it at 40 - 45 and see if I can get better climb.Jack PhillipsNX899JPRaleigh, NC _____
Stall speed (either power-on or power-off) occurs at a HIGHER airspeed athigher weight. That's why performance figures for certified aircraft aretypically shown at gross weight. Think about it, if the stall speed wentdown as the weight goes up, you could therorectically add enough weight soit would never stall, and the fatter the pilot the better the shortfieldperformance would be. The stall actually occurs at the critical angle ofattack (which is a function of the airfoil design), regardless of airspeed.That's why you can get into an accelerated stall at high airspeeds (such asentering a snap roll, or pulling out of a steep dive). For this reason, anAOA meter is a better indication of impending stall than an airspeedindicator, but since they tend to be more expensive, we use the airspeed asthe indication.I've always climbed my Piet at 50 - 55 mph, and get between 100 and 500 fpmdepending on loading and density altitude. Maybe tomorrow I'll do some testflying and try it at 40 - 45 and see if I can get better climb.Jack PhillipsNX899JPRaleigh, NC _____
Pietenpol-List: Re: Kringle's Curious Question about projects
Original Posted By: shad bell
Awesome website! Thanks Mike--------JohnRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Tue, 22 Jun 2010 12:04:50 -0700 (PDT)
Awesome website! Thanks Mike--------JohnRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Tue, 22 Jun 2010 12:04:50 -0700 (PDT)
Pietenpol-List: Re: Corvair powered Piet in Spain...
Original Posted By: "GliderMike"
I disagree with the statement that an aircraft will stall at a lower airspeed withan aft cg. I knew skydivers that wouldn't jump a "Lodestall," oops, I meanta Lodestar, because they tended to stall if the airspeed was reduced much duringexits. As the jumpers moved to the back of the aircraft, the cg becamevery much aft. I've heard more than one story about a Lodestar rolling over onits back like a cheap hooker as a group of skydivers got out. Beech 18's werebad about that also, but not as bad as the "Lodestall."--------HOMEBUILDERWill WORK for SpruceLong flights, smooth air, and soft landings,GliderMike, aka Mike GlasgowRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Corvair powered Piet in Spain...
I disagree with the statement that an aircraft will stall at a lower airspeed withan aft cg. I knew skydivers that wouldn't jump a "Lodestall," oops, I meanta Lodestar, because they tended to stall if the airspeed was reduced much duringexits. As the jumpers moved to the back of the aircraft, the cg becamevery much aft. I've heard more than one story about a Lodestar rolling over onits back like a cheap hooker as a group of skydivers got out. Beech 18's werebad about that also, but not as bad as the "Lodestall."--------HOMEBUILDERWill WORK for SpruceLong flights, smooth air, and soft landings,GliderMike, aka Mike GlasgowRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Corvair powered Piet in Spain...
Pietenpol-List: performance numbers and stall speeds vs. a/c weight
Original Posted By: "Tim White"
Like Mikee, I have found that my Air Camper almost will notstall with power on. I usually climb it to at least 2500-3000'to play with stalls and it's always nice and cool up thathigh, so I don't know what it will do down low and hotbut in controlled stall testing with power on, I can getthe nose pointed VERY high up and hold it there with theASI indicating down in ranges where it is obviously notaccurate (in the low 30s, even high 20s, but with needlejumping due to buffet or propwash). If I hold 'er steady,the nose will not drop or bob, and it won'tfall off to either side if I stay on the rudder. Just asteady mush. It takes a lot of nerve to hold the stickall the way back and power full on like that though.I have not tried it with the A75 yet... those experienceswere with the 65.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net ________________________________________________________________________________
Like Mikee, I have found that my Air Camper almost will notstall with power on. I usually climb it to at least 2500-3000'to play with stalls and it's always nice and cool up thathigh, so I don't know what it will do down low and hotbut in controlled stall testing with power on, I can getthe nose pointed VERY high up and hold it there with theASI indicating down in ranges where it is obviously notaccurate (in the low 30s, even high 20s, but with needlejumping due to buffet or propwash). If I hold 'er steady,the nose will not drop or bob, and it won'tfall off to either side if I stay on the rudder. Just asteady mush. It takes a lot of nerve to hold the stickall the way back and power full on like that though.I have not tried it with the A75 yet... those experienceswere with the 65.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net ________________________________________________________________________________