Why no red zone below the stall speed on the ASI?

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docmirror

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We know there is a redline speed on all ASIs, it's at the Vne. But, being slower than stall speed is just as bad, if not worse. Makes me think there should be a red zone, and maybe even a transition yellow zone where the speed drops below controllable without adding flaps.

Things that make me go - hmmmmmmm...
 
Because a plane can be stalled an any airspeed.
 
Get a lift reserve indicator.

Admittedly, I could have lived without it on our 180 since I fly by feel when I get real slow, but I like it as a backup. I can see where one would be real good for a faster plane with a higher alpha wing and harder stall break.

I think they just eased the STC restrictions on them for GA. We should be seeing more of them.
 
Red on aircraft gauges is bad and is generally somewhere the needle should never be. There are plenty of reasons the needle would be in the red therefore red is not an appropriate indication.
 
jesse said:
Red on aircraft gauges is bad and is generally somewhere the needle should never be. There are plenty of reasons the needle would be in the red therefore red is not an appropriate indication.
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The kicker is that the airspeed tape on our Piper has a red zone below Vs.
 
jesse said:
Red on aircraft gauges is bad and is generally somewhere the needle should never be. There are plenty of reasons the needle would be in the red therefore red is not an appropriate indication.
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You mean like when you are stopped on the ground, slow taxi, etc. Sure, the red is not useful in ground ops. But planes are for the air, and when in the air, a speed below unaccelerated stall is just as fatal, sometimes worse than the redline at the upper end of the ASI.
 
There already is a stall horn and aerodynamic buffeting to warn you, how much more do you need?

Hopefully you won't keep hauling back like the Air France guys. ;)
 
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docmirror said:
You mean like when you are stopped on the ground, slow taxi, etc. Sure, the red is not useful in ground ops. But planes are for the air, and when in the air, a speed below unaccelerated stall is just as fatal, sometimes worse than the redline at the upper end of the ASI.
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I frequently do slow flight with the ASI reading zero. I'm not dead (yet).
 
docmirror said:
We know there is a redline speed on all ASIs, it's at the Vne. But, being slower than stall speed is just as bad, if not worse. Makes me think there should be a red zone, and maybe even a transition yellow zone where the speed drops below controllable without adding flaps.

Things that make me go - hmmmmmmm...
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Airbus solved that problem:

pfda320_zpse1098f4c.jpg


airbusspeedtape_zps5cf2457d.jpg


airbusspeed_zps1683e24e.jpg




Vα prot, Vα floor, Vα MAX vary according to weight and configuration.
To deactivate the angle of attack protection, the pilot must push the sidestick:
‐ Greater than 8 ° forward, or,
‐ Greater than 0.5 °for at least 0.5 s when α < α MAX.
In addition, below 200 ft, the angle of attack protection is also deactivated, when:
‐ Sidestick deflection is less than half nose-up, and
‐ Actual α is less than α prot – 2 °.
Note: 1. At takeoff α prot is equal to α MAX for 5 s.
2. αfloor is activated through the A/THR system, when:
‐ α is greater than αfloor (9.5 ° in configuration 0; 15 ° in configuration 1, 2; 14 ° in
configuration 3; 13 ° in configuration FULL) or
‐ Sidestick deflection is greater than 14 ° nose up, with either the pitch attitude or the
angle-of-attack protection active.
The αfloor function is available from lift-off to 100 ft RA before landing.
 
docmirror said:
We know there is a redline speed on all ASIs, it's at the Vne. But, being slower than stall speed is just as bad, if not worse. Makes me think there should be a red zone, and maybe even a transition yellow zone where the speed drops below controllable without adding flaps.

Things that make me go - hmmmmmmm...
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Get in a more powerful aircraft solo or with just an instructor and see just how slow you can fly it level.

I did this in an Archer, at 48 knots. Clean stall speed in the POH is 50.
 
Just how many red and yellow zones do you need? More is not always better.
For the record, I only have one red line on my ASI in the Champ.
 
MAKG1 said:
Get in a more powerful aircraft solo or with just an instructor and see just how slow you can fly it level.

I did this in an Archer, at 48 knots. Clean stall speed in the POH is 50.
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CAS or IAS?
 
MAKG1 said:
Get in a more powerful aircraft solo or with just an instructor and see just how slow you can fly it level.

I did this in an Archer, at 48 knots. Clean stall speed in the POH is 50.
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More powerful than what? I already have 40 extra horses. At the risk of overheating my engine, I can pretty much hang it on the prop now.
 
docmirror said:
But planes are for the air, and when in the air, a speed below unaccelerated stall is just as fatal, sometimes worse than the redline at the upper end of the ASI.
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I'm thinking that stalls and stalling get demonized a bit in our training and in what most of us would consider normal operations.

For example, spins (rotating stalled aircraft) used to be part of basic training and many aircraft were permitted to do them. Not only could spins be fun but in extreme circumstances, even useful. Spinning down through an undercast is an effective way to get down to visual conditions above the ground given enough ceiling height. More than a few airmail pilots survived being trapped on top or in cloud by spinning out. I practiced them in sailplanes where certain mountain wave conditions could trap one on top. As long as the ASI remains below Vs, all is good as long as ground contact is avoided.

On the other hand, losing visual reference and entering a spiral can quickly lead to exceeding Vne and eventual destruction of the aircraft independent of ground contact.

It seems like much training is focused on impending stall detection and avoidance. Spinning is not part of basic training and many trainers are not certified for such manuevers. We even have an aircraft where spin recovery calls for sacrifice of the aircraft.

I'm thinking the red paint is in the right place.
 
docmirror said:
You mean like when you are stopped on the ground, slow taxi, etc. Sure, the red is not useful in ground ops. But planes are for the air, and when in the air, a speed below unaccelerated stall is just as fatal, sometimes worse than the redline at the upper end of the ASI.
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This has already been stated but repeat after me: STALLS ARE NOT DETERMINED BY AIRSPEED. The FAA requires other warnings for stalls that are determined by the angle of attack approaching the critical angle.
 
docmirror said:
We know there is a redline speed on all ASIs, it's at the Vne. But, being slower than stall speed is just as bad, if not worse. Makes me think there should be a red zone, and maybe even a transition yellow zone where the speed drops below controllable without adding flaps.

Things that make me go - hmmmmmmm...
Click to expand...

If the was a red zone near VS, you could not take off without violating that value.
 
Kelvin said:
No such thing...:D
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Huh? "horses" is a common euphemism for horse power. Sorry if it was not engineering-speak, I try to keep it light, but of course - there are folks here with both the anal, and the retentive issue. :wink2:
 
docmirror said:
Huh? "horses" is a common euphemism for horse power.
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Right on. I get that...

docmirror said:
Sorry if it was not engineering-speak, I try to keep it light, but of course - there are folks here with both the anal, and the retentive issue. :wink2:
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Don't let the elegant avatar picture throw you...the glasses are so I can read...Doc, I am not "that guy"..I am a redneck who truly believes there is no such thing as excess horsepower...:yes:
 
flyingron said:
STALLS ARE NOT DETERMINED BY AIRSPEED. The FAA requires other warnings for stalls that are determined by the angle of attack approaching the critical angle.
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I'M GLAD YOU SHOUTED THIS, CUZ IT'S PARTLY WRONG. IF I AM IN A 45DEG BANK, I CAN USE ANY AIRSPEED AND STALL? IF I LOAD THE PLANE TO GROSS AND STALL, AND THEN LOAD IT TO MINIMUM WEIGHT AND STALL, AM I AT THE SAME AIRSPEED? AIRSPEED PLAYS NO PART IN THE STALL EQUATION? WING LOADING/AOA IS NOT AFFECTED BY AIRSPEED? HMMMMMMMMM......
 
Kelvin said:
Right on. I get that...



Doc, I am not "that guy"..I am a redneck who truly believes there is no such thing as excess horsepower...:yes:
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That's why I got 40 more than the factory put on. Power is good, more power is more gooderer.
 
ARFlyer said:
The kicker is that the airspeed tape on our Piper has a red zone below Vs.
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I think many/most? airplanes with an airspeed tape have a red zone below stall speed.

0.jpg


So I think the answer to the OP's question why there is no red line on a round-dial aircraft airspeed indicator is that it is convention.
 
I haven't been a CFI for a long time, but IIRC the bottom of the green arc is Vs and the bottom of the white arc is Vso. It's there for your entertainment purposes only. :)
 
Everskyward said:
I think many/most? airplanes with an airspeed tape have a red zone below stall speed.

0.jpg


So I think the answer to the OP's question why there is no red line on a round-dial aircraft airspeed indicator is that it is convention.
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I didn't know that, quite interesting. I'm going to check the new EXP MFDs and see what they do.

<edit; Grand Rapids does provide a red zone below whatever speed you put in as your lowest setpoint when configured. Which I guess would be the level unaccelerated stall speed dirty. I'm guessing the other vendors do the same. Kewl>
 
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docmirror said:
I didn't know that, quite interesting. I'm going to check the new EXP MFDs and see what they do.
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My GRT HX EFIS has a red ladder displayed when below stall speed... but in practice, every flight ends up with lots of red airspeeds before landing. And in practice, I never see it.

I know a lot of people like AOA indicators but I'm glad I have a stall warning vane and horn. A very simple and effective angle of attack warning system.
 
docmirror said:
That's why I got 40 more than the factory put on. Power is good, more power is more gooderer.
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But it's not extra, not until time starts warping and matter expands into infinity and you depart the universe. Now you have extra power.:D until then you just have "more".
 
docmirror said:
I'M GLAD YOU SHOUTED THIS, CUZ IT'S PARTLY WRONG. IF I AM IN A 45DEG BANK, I CAN USE ANY AIRSPEED AND STALL? IF I LOAD THE PLANE TO GROSS AND STALL, AND THEN LOAD IT TO MINIMUM WEIGHT AND STALL, AM I AT THE SAME AIRSPEED? AIRSPEED PLAYS NO PART IN THE STALL EQUATION? WING LOADING/AOA IS NOT AFFECTED BY AIRSPEED? HMMMMMMMMM......
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You REALLY need to understand this. Angle of attack -- and only angle of attack -- determines stall. "Stall speeds" are a proxy for angle of attack under specific conditions.

If you yank the elevator hard enough, you can quite easily stall well above the "stall speed" without waiting to slow down.

The stall speed is lower at lower weights. The stall angle of attack is not.
 
MAKG1 said:
You REALLY need to understand this. Angle of attack -- and only angle of attack -- determines stall. "Stall speeds" are a proxy for angle of attack under specific conditions.

If you yank the elevator hard enough, you can quite easily stall well above the "stall speed" without waiting to slow down.

The stall speed is lower at lower weights. The stall angle of attack is not.
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I REALLY DO UNDERSTAND THIS.


But - thanks for shouting. :mad2::no:
 
I can plainly see why the LRI is superior to an ASI because on different days in VMC at the same field, I will see different ground speeds on approaches while keeping the blue dot illuminated.

This is to be expected with changes in density altitude, but it never became so clear until I flew with an AOA.

I like the fact that no matter how I'm loaded, or what the density altitude is, if the blue dot says fly 65knots on approach instead of 55, that's what you do. It works in the reverse. Sometimes, the ASI will be bouncing with zero lock, not reliable really, and it feel's like you're going to fall out of the sky you're GS is so slow, but the blue dot says keep it there. Those are the cool, perfect air headwind days when you're light and flying right, and you fantasize you're a Valdez STOL champion ... ;):D
 
More importantly. Why do you feel you need it?
 
badges? we don't need no stinking badges! ..

desertav8r said:
More importantly. Why do you feel you need it?
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If you're asking me, I didn't need it. I wanted it.

The system was less than $1500.00 installed. :dunno: I can afford that. Besides, you don't buy a skywagon and not mod it... The AOA was a pittance compared to the S-TEC 30, 430W, GPSS, Sportsman STOL, H.I.D. wingtip wags, B.A.S. shoulder harnesses and a winking eye dog on the dash ...

Would I do an AOA on it again? Yep. I can see where it would be more useful for a higher alpha wing. If I were transitioning to say a Glasair III, I would sure like it if it had one. It would take some of the workload out of it for me. Just keep it at or above the blue dot, and joy to the world. :)
 
I just don't get it I guess. Fly by feel or fly by toys. I prefer feel in a GA aircraft. Otherwise it's not enjoyable to me.

Not saying you're wrong. It's just not my cup of tea.
 
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