corner airspeed list for all aircraft

[BravoT]

I was intrigued by the comment that AH uses TAS for all performance aspects, and said to myself "That can't be right when it comes to stall speeds".  So I did a little test offline:

Spit 16, 50% fuel

Takeoff, stay on the deck, autopilot on, cut the engine - Stall horn fires at 100 IAS.
5,000 feet - Stall horn fires at 100 KIAS
10,000 feet - Stall horn fires at 100 KIAS
20,000 feet - Stall horn fires at 100 KIAS

Only on the deck at TAS and IAS the same.  So beware to the AH pilot who's watching the red needle rather than the white one....

[TequilaChaser]

I can't speak to what is used in or modelled in AH, but in the real world the only stall speed that a pilot worries about is IAS.  The IAS stall speed does not change with altitude.

The TAS airspeed increase with altitude, but airspeed indicators in the real world don't display TAS in any manner that is useful to a pilot to figure out if he is approaching stall speed.  The reason is quite simple - TAS is a function of air density.  A pilot would need to constantly recalculate his TAS (and in WWII the only way to do that would be by way of an E6B) in order to figure out whether he's about to fall out of the sky, whereas IAS stall speed is the same regardless of the surrounding environment.

I appreciate that AH is not the real world, but to say that stall speed increases with altitude is simply not correct unless you specify TAS.  And while performance charts do indeed specify TAS, POH specify IAS when it comes to stall speeds.

oops, my bad for not including the specifically for TAS part!  I should not have even made a reply/post to this thread .......... I am sure that any POH will read exactly as it needs too whether it is TAS or whether the particular subject at hand needs to be in IAS...  I do not recall ever saying anything about POH's

Also, I never posted that people fly around watching the Red Needle and I also said when teaching we do use IAS........  I specifically said that plane performance data/comparison charts, etc.. refer to TAS instead of IAS  both in RL and in AH...


regarding your stall testing, did you also try for the 50,000 ft test you previously mentioned regarding IAS?  or even 45,000 ft, 40,000 ft, 35,000 ft, 30,000 ft, 25,000 ft for your IAS comparison

I am curious how your Spit XVI will do at the different alts with 50% fuel........ you can go offline and set your fuel burn rate to 0.001 and film your test so others can see the results if you dont mind posting the film

I was intrigued by the comment that AH uses TAS for all performance aspects, and said to myself "That can't be right when it comes to stall speeds".  So I did a little test offline:

again, I only posted that AH's ( & RL ) speed charts / climb charts / Energy Management charts  all use TAS for their speed

I will end my participation in this thread now, with this last sentence ^^^

edit:  btw,, welcome to Aces High if you are New to AH,  

what might your gameid be online ?   I haven't seen a BravoT   online before........    are you new to AH?  or just under a different bbs username and in game  gameid?


TC

[pembquist]

So the thing with the TAS and the IAS is not as important as the AOA but we don't have an AOA indicator in AH2 so phooey.  What I want to know is if its 2.4 times the clean stall speed does that work using IAS and TAS? So like this: Alt 5' stall 100 IAS 100 TAS, corner speed 240 TAS or IAS.  Alt 80,000' stall 100 IAS 800 TAS corner speed 240 IAS 1920 TAS?  (The values of IAS and TAS are for examplification here.)  So can we use either one? (which would mean using IAS because thats the big needle that my beady little eyes can see.)

[Rolex]

TAS increases about 2% for each thousand feet of altitude, so let's say a plane has a clean stall speed of 100 MPH. At 20,000' MSL, that would be a difference of about 40 MPH from IAS. IAS would read about 40 MPH slower than TAS, but the IAS stall speed is still the same. That's why it's called "indicated," because it's not "true." 

A difference of 40 MPH is a pretty tough number to discern on an AH cockpit gauge. That's only 24 MPH difference at 12,000' MSL, an even more difficult number to read. Not too many fights start above that in the Main Arenas. The greater question is whether corner speed is something to be concerned about. I would say not really for the defensive maneuvering example given. A little high yo-yo by the aggressor trumps a 6G pull at corner speed every time.

Corner speed is more relevant to jets than to the planes in AH. The TAS/IAS modeling question is valid, though.

[FLS]

So the thing with the TAS and the IAS is not as important as the AOA but we don't have an AOA indicator in AH2 so phooey.  What I want to know is if its 2.4 times the clean stall speed does that work using IAS and TAS? So like this: Alt 5' stall 100 IAS 100 TAS, corner speed 240 TAS or IAS.  Alt 80,000' stall 100 IAS 800 TAS corner speed 240 IAS 1920 TAS?  (The values of IAS and TAS are for examplification here.)  So can we use either one? (which would mean using IAS because thats the big needle that my beady little eyes can see.)

The stall horn and stall buffet are both AOA indicators.  You stall at the same AOA regardless of speed.

[BravoT]

oops, my bad for not including the specifically for TAS part!  I should not have even made a reply/post to this thread .......... I am sure that any POH will read exactly as it needs too whether it is TAS or whether the particular subject at hand needs to be in IAS...  I do not recall ever saying anything about POH's

Also, I never posted that people fly around watching the Red Needle and I also said when teaching we do use IAS........  I specifically said that plane performance data/comparison charts, etc.. refer to TAS instead of IAS  both in RL and in AH...


regarding your stall testing, did you also try for the 50,000 ft test you previously mentioned regarding IAS?  or even 45,000 ft, 40,000 ft, 35,000 ft, 30,000 ft, 25,000 ft for your IAS comparison

I am curious how your Spit XVI will do at the different alts with 50% fuel........ you can go offline and set your fuel burn rate to 0.001 and film your test so others can see the results if you dont mind posting the film


again, I only posted that AH's ( & RL ) speed charts / climb charts / Energy Management charts  all use TAS for their speed

I will end my participation in this thread now, with this last sentence ^^^

edit:  btw,, welcome to Aces High if you are New to AH,  

what might your gameid be online ?   I haven't seen a BravoT   online before........    are you new to AH?  or just under a different bbs username and in game  gameid?


TC

I'm BravoT in the MA.  I've been around for a few months, but first time posting in the forums.

IAS stall speed will be the same regardless of altitude.  But no, I didn't bring the Spit up above 20K.  Weight will effect stall speed, but the IAS stall speed will still be the same at all altitudes.

Someone did make the point in this thread, however, that a stall is actually  function of AOA rather than speed (which is why pilots are taught that they can stall at any speed at any altitude and at any attitude).  But the airspeed indicator is generally used as the most direct instrument to provide info about when a stall will occur, and an ASI is calibrated to show IAS.

Also keep in mind that the IAS stall speed will increase as G loading increases.  In a 60 degree bank, the IAS stall speed will be the clean and level stall speed multipled by approximately 1.4.  So in an aircraft with a clean stall speed of 100 KIAS, you need to be doing 140 KIAS in order to sustain a 60 degree bank without losing altitude.

[FLS]

I believe the 1.4 multiplier is for a 45 degree bank. A level 60 degree bank would be 2G.

[BravoT]

I believe the 1.4 multiplier is for a 45 degree bank. A level 60 degree bank would be 2G.

A level 60 degree bank is indeed 2 Gs, but to get the stall speed you use the square root of the G load (roughly 1.4).

[pembquist]

Its probably to late in the thread to get an answer but I realize my question wasn't worded to well so I'll try to simplify.  Will my corner speed in IAS be approximately 2.4 x IAS of clean stall.  This corner speed being valid for one weight condition no flaps but pretty much all altitudes?

not to quibble but by aoa indicator I meant something like this The stall horn and buffet don't have much of a range in their display.

[FLS]

A level 60 degree bank is indeed 2 Gs, but to get the stall speed you use the square root of the G load (roughly 1.4).

Thanks. I knew that but I responded without thinking about what you were saying.   

Pembquist to answer your question, yes. You can just multiply 2.4, the square root of the 6G pilot limit, by the stall speed at your current weight.

What did you want to use AOA for that you can't do with the G load?

[pembquist]

Hi FLS.  Thanks for the straightforward answer.  I'm sorry to be confusing but I didn't  want an AOA instrument I was just blabbing. I have always wanted an AOA for the plane I'm building so that desire probably leaked out here.  It seems like a much better instrument for avoiding stalls as its easy to interpret and requires no compensation for loading.  It also gives an indication of how much lift you have in reserve.  This wouldn't probably be very useful in AH so apologies for this little rabbit hole.  Cheers!

[FLS]

AOA determines your coefficient of lift but the actual lift is a function of airspeed which is why your speed is your best indication of "reserve" lift. Just keep in mind, as BravoT pointed out, that stall speed increases as bank angle increases.

Also to clear up some confusion, I mentioned altitude in regard to corner speed. You still get your best rate and radius at the same IAS corner speed. However, altitude increases the turn rate degrees per second and turn radius at corner speed because the true airspeed is higher.

Edited for clarity and accuracy.

[pembquist]

I have to stop reading this thing.  I'm beginning to feel like a pedantic nitwit but regardless I would have to disagree that the Airspeed is the best indicator of reserve lift.  Having just written this I realize you are talking about Aces High and I'm still stuck on the real world so apologies for beating a dead horse.  The great thing about an angle of attack indicator is that it tells you how much angle you have before you reach your maximum coefficient of lift, separation and stall.  It doesn't matter what your speed is, how much you weigh, what your bank angle is, how many g's your pulling, whether your going up,down or level.  Here is a nice one http://www.advanced-flight-systems.com/Products/AOA/aoa.html

In level flight as your speed goes up your aoa goes down and vice versa so airspeed is a good proxy for aoa.  On the other hand speed is quickly understood as the energy/inertia state of the aircraft. For both of these reasons speed could well be considered to be an indicator of 'reserve lift' in the sense of reserve ability to go up.  However what airspeed won't tell you, without more information and calculation is how close you are to stalling if you are going 150 knots in a 45 degree bank turn, nor if you are going 60 knots on approach.  The AOA indicator will, at a glance.  Since stalling is basically running out of lift I feel that the AOA indicator is a direct, (and therefore superior,) indicator of how much lift your wing has before it runs out, ergo how much 'reserve lift'.   Further all the little V numbers shown on the Airspeed indicator are only accurate at one weight and balance condition and 0 G.  The corresponding angle of attack remains the same regardless.  I believe that if general aviation aircraft had AOA indicators there would be less of the classic stall spin accidents happening.

The sad thing is none of this helps me fly my fighter plane any better.  So I will now shut up and sit down.

Cheers!

[BravoT]

The sad thing is none of this helps me fly my fighter plane any better.  So I will now shut up and sit down.

Cheers!

Ain't that the truth.. Conversely, do you know how hard it is to check your six in a 172?