CIRRUS TRAGEDY

[tmo]

FWIW, the M20K-231 POH lists a stall speed of 89.5 KIAS in 60 degree bank, clean config, 2900 lbs.  Goes down to 79 at 2300 lbs, and 84/74 respectively with full flaps.  Still a good 24, 25 knots faster than straight-and-level.

[kortopates]

1 hour ago, philiplane said:

WOW. I'm not sure what Cirrus you flew, but it certainly doesn't behave like any of the 200 or so that I have flown.

The stall speed for an SR20 at gross weight is only 56 knots. 65 knots with no flaps. At training weights those numbers are even lower. Traffic pattern speeds are essentially the same as any other fixed gear piston single trainer. 

The stall speed at a 60 degree bank angle is 90 clean, 81 with full flaps. It's such an unusual combination that you'd have to be doing mild aerobatic training to get anywhere near that number in normal flight. We don't even come close to it doing commercial pilot training maneuvers with poorly trained private pilots. In the more common bank angles of 30-45 degrees, the stall speed is still only 57-64 knots with full flaps, and 68-78 clean. 

A 172 that stalls at 50 knots clean & level, stalls at 70 knots clean in a 60 degree bank. So that's a 20 knot rise for the 60 degree bank angle. The Cirrus has a 25 knot rise. WOW. 5 KNOTS MORE. 

I've always found the stall characteristic of a Cirrus to be well-mannered, and more maneuverable than a Cessna. They are similar to a Cherokee in a stall, where the nose bobs and finally drops a bit, with no tendency to drop a wing suddenly like a 172. You have full aileron control in a stall, unlike a Cessna, where you need the rudder or you'll enter a spin quickly. 

If you were uncomfortable, you suffered from a poor introduction to the plane by the instructor.

I agree, and its split wing enables  the ailerons to be much more effective near the stall than any of our other trainers - which adds a level of forgiveness we don't have in the Mooney. 

[Ibra]

I think for a better and fair comparison of trainers one need to look at 1/ slow stall speed VS AND 2/ sink rate or power to fly 5kts-10kts above stall AND 3/ uncoordinated ailerons use near stall, the SR20 has 3/, C172 has 1/ & 2/, PA28 Warrior seems to have all 1/, 2/, 3/ 

Technically, stall speed % changes in turn has nothing to do with aircraft type or bank angle, it is purely associated with weight and G-load, in level flight G-load and bank angle are related, but on a VFR circle to land or base to final turn I am assuming people are still going down at 1G and -500fpm? 

If one wants to fly a tight turn (as opposed to steep turn), Cirrus or anything else, they are better with 1.3*VS & 45deg & 1G pitch down while keeping low power and take some rate of descent, while I would not advise doing this for a check ride with DPE (one should always aim to make well planned pattern & turn or just go-around) but at some point one need to know how to “over-bank” safely?

Edited May 25, 2020 by Ibra

[kortopates]

On 5/25/2020 at 8:48 AM, tmo said:

FWIW, the M20K-231 POH lists a stall speed of 89.5 KIAS in 60 degree bank, clean config, 2900 lbs.  Goes down to 79 at 2300 lbs, and 84/74 respectively with full flaps.  Still a good 24, 25 knots faster than straight-and-level.

Keep in mind that those stall speeds are for level unaccelerated 1-g flight. When flying a standard FAA pattern discussed in the FAA Handbook or Aeronautical Knowledge that supposedly we were all taught, we're never level but descending through all our turns in the traffic pattern after the downwind. Thus the wings are only lightly loaded and AOA is greatly reduced lowering our stall speed. Still no need to do 60 bank turns, but we can do them while descending. But especially no need to fear  a 30 degree bank in the pattern. Pilots should be more aware of AOA, in that it takes both bank and loading the wing to stall it. Not bank alone and therefore they should really fear the 747 pattern! The great irony in my opinion is that we have pilots that are flying long non-standard patterns out of fear of over-banking and armed with only the knowledge of bank angle vs stall. But looks what actually happens, they are so far away from the airport that they're no longer able to make descending turns with the wings lightly loaded much like the above Cirrus tragedy and are making all there turns with the wings level and fully loaded which is making them an order of magnitude more vulnerable to traffic pattern stalls than if they would just learn to how to do a standard traffic pattern. Very few of these accidents are actually from close in patterns where the pilot skidded from being blown across final, most are actually from maneuvering while level and getting low and slow and thus loading the wing up. Further such pilots will likely be very unequipped to make a power off landing in an emergency.

Edited May 26, 2020 by kortopates
corrected "unaccelerated"

[brndiar]

 

 

7 minutes ago, kortopates said:

Keep in mind that those stall speeds are for level accelerated 1-g flight. When flying a standard FAA pattern discussed in the FAA Handbook or Aeronautical Knowledge that supposedly we were all taught, we're never level but descending through all our turns in the traffic pattern after the downwind. Thus the wings are only lightly loaded and AOA is greatly reduced lowering our stall speed. Still no need to do 60 bank turns, but we can do them while descending. But especially no need to fear the a 30 degree bank in the pattern. Pilots should be more aware of AOA, in that it takes both bank and loading the wing to stall it. Not bank alone and therefore they should really fear the 747 pattern! The great irony in my opinion is that we have pilots that are flying long non-standard patterns out of fear of over-banking and armed with only the knowledge . But looks what actually happens, they are so far away from the airport that they're no longer able to make descending turns with the wings lightly loaded much like the above Cirrus tragedy and are making all there turns with the wings level and fully loaded which is making them an order of magnitude more vulnerable to traffic pattern stalls than if they would just learn to how to do a standard traffic pattern. Very few of these accidents are actually from close in patterns where the pilot skidded from being blown across final, most are actually from maneuvering while level and getting low and slow and thus loading the wing up. Further such pilots will likely be very unequipped to make a power off landing in an emergency.

Hi,

when you are in descent, relative wind is from below, AOA rise.

lg,m

[Ibra]

If you are not touching the power, it depends if your rate of descent is obtained by flying faster? or slower? in the latter aircraft nose goes up and AoA increase as well as descent rate, in the former aircraft nose goes down and AoA decrease as well as descent rate, most people will fly their pattern descent using the former: by pointing aircraft nose to the ground to descend and it will fly on low angle of attack (close to the angle between aircraft nose axis and aircraft motion) when they are passing near the threshold they may switch to the latter...

Edited May 25, 2020 by Ibra

[brndiar]

14 minutes ago, Ibra said:

If you are not touching the power, it depends if your rate of descent is obtained by flying faster? or slower? in the latter aircraft nose goes up and AoA increase as well as descent rate, in the former aircraft nose goes down and AoA decrease as well as descent rate, most people will fly their pattern descent using the former: by pointing aircraft nose to the ground to descend and it will fly on low angle of attack 

AOA is difference between where the plane points and were it flyes. Just a battle of the words.

For me, the biggest problem is, that people take their two dimensional 1 G world in air and consider the  turn as a a change in heading over the ground. Something like to drive a car, they want to fly "level".

For a plane a turn is any  change in the velocity vector of the airplane. When we pull up the nose, that is a turn because the airplane is now flying in a different direction. When we push, that s also a turn. A turn is always accomplished by changing the lift being produced by the wing. And here is, where  problem arises.

 

lg,m,

Edited May 25, 2020 by brndiar

[ilovecornfields]

33 minutes ago, kortopates said:

Keep in mind that those stall speeds are for level accelerated 1-g flight. When flying a standard FAA pattern discussed in the FAA Handbook or Aeronautical Knowledge that supposedly we were all taught, we're never level but descending through all our turns in the traffic pattern after the downwind. Thus the wings are only lightly loaded and AOA is greatly reduced lowering our stall speed. Still no need to do 60 bank turns, but we can do them while descending. But especially no need to fear the a 30 degree bank in the pattern. Pilots should be more aware of AOA, in that it takes both bank and loading the wing to stall it. Not bank alone and therefore they should really fear the 747 pattern! The great irony in my opinion is that we have pilots that are flying long non-standard patterns out of fear of over-banking and armed with only the knowledge . But looks what actually happens, they are so far away from the airport that they're no longer able to make descending turns with the wings lightly loaded much like the above Cirrus tragedy and are making all there turns with the wings level and fully loaded which is making them an order of magnitude more vulnerable to traffic pattern stalls than if they would just learn to how to do a standard traffic pattern. Very few of these accidents are actually from close in patterns where the pilot skidded from being blown across final, most are actually from maneuvering while level and getting low and slow and thus loading the wing up. Further such pilots will likely be very unequipped to make a power off landing in an emergency.

I think you meant “UNaccelerated  1-g flight” but the rest of that is EXACTLY what I’ve seen (and occasionally done) and I think you hit the nail right on the head.

Anytime I even think I might be slow in the pattern the first thing I do is unload the wings. I wonder if an unusual attitude course were required for the private pilot rating what effect that would have on LOC-I accidents? I did mine almost 20 years ago and still remember the importance of “unloading the wing.” Being at the top of a hammerhead turn with almost no airspeed but not stalled really illustrates the point of AOA being the important factor, not speed or bank angle (and it’s really fun pointing straight down at the top of the turn and pulling out of the dive!)

I think you’re absolutely right that people fixate on bank angle (not the problem) and ignore AOA (the actual problem that kills them). I don’t remember reading about wings stalling because  they exceeded the critical bank angle...

[Ibra]

7 minutes ago, brndiar said:

For me, the biggest problem is, that people take their two dimensional 1 G world in air and consider the  turn as a a change in heading over the ground. Something like to drive a car, they want to fly "level"

Add to that the 3D jet fighter syndrome, if I point the nose to X the aircraft goes to X 

 

[Ibra]

40 minutes ago, ilovecornfields said:

Anytime I even think I might be slow in the pattern the first thing I do is unload the wings. I wonder if an unusual attitude course were required for the private pilot rating what effect that would have on LOC-I accidents?

Just doing wingovers and chandelles (I think commercial does it?) would open the eye on the important of unloading the wings in crazy large bank & slow speeds, for flying with AoA indicators I doubt much of it will help without understanding the underlying physics “speed & bank & load”: it helps to know how far you are from stall in any configuration but it will be hard to stay in G-V & H-V flying envelops looking solely at AoA only...

This SR20 had probably a big AOA indicator down left on the PFD (at least on new G1000 models) it still does not tell one how to avoid stalling in a turn as much as “min speed & max bank & max load” does 

[Ross Taylor]

The only thing I found uncomfortable about the two Cirrus I've flown is the left-side side yoke.  As a lefty, I found it really awkward to try and write anything down without the AP on.  But that was my only "complaint" about the flying part...other than that, they were docile well-mannered aircraft.

[Vance Harral]

I think there is a small but important misconception in the well-intentioned posts above: some of them appear to imply that a descending aircraft is always "unloaded".  If that was the intent, it's not correct.

An aircraft in a constant rate, level descent will experience a 1G load on the wings, same as in level flight.  An aircraft in a 30/45/60 degree turn executed in a constant rate descent will experience a 1.15/1.41/2.00G load on the wings, same as in level turns.  You don't "buy" anything in terms of reduced load factor just by being in a descent.

If you change your rate of descent by pushing or pulling on the yoke, you do change AOA and load factor.  So the instinct to "push and unload" if you're worried about a stall is a good one.  Letting the nose drop in a turn so as to increase the rate of descent as the turn is executed is similarly effective.  But it's the vertical acceleration that helps you, not the vertical velocity.  Put another way, if you make a bad decision and snatch back on the yoke because you were startled, your odds of instantly exceeding the critical AOA and stalling are the same regardless of whether the aircraft was level, descending, or climbing when you did so.

The idea that an aircraft in a constant rate descent has a lower G-loading than an aircraft in level flight, or in a climb, is a common misconception.  But an aircraft with a constant bank angle and constant rate of climb or descent (including zero) experiences the same G load, regardless of its vertical velocity.  The mathematical explanation is just Newtonian physics: F=MA.  If the vertical acceleration (A) is zero, the net up/down force (F) is zero.  Vertical velocity is not a factor in the equation.  Therefore, load factor only changes when a climb or descent is initiated, not once it's established.

 

Edited May 26, 2020 by Vance Harral
correct spelling error, no change in content

[Ibra]

57 minutes ago, Vance Harral said:

The idea that an aircraft in a constant rate descent has a lower G-loading than an aircraft in level flight, or in a climb, is a common misconception

Yes it is temporary, the only way to keep a continuous turn going unloaded is to take a huge rate of decent with airspeed building up quickly but I am assuming we are after lesa than 90deg headings change when one is turning in the pattern? Some do ideed fly 180deg heading change in deep Canyons well banked and lightly loaded but it surely "umloading the wings" does not make sense for continuous N×360s turns going forever you have to cut power and take it back...

At 45deg bank you will be getting close to VNE after few unloaded 360 turns: you gain 17kts per unloaded G for each second (so about second 360 turn in 1G spiral 6kts/second or first 360 turn in 0G spiral 25kts/second)

Also another disclaimer: don't unload the wings to make 180 back to the runway after an EFATO with tailwind, landing straight into wind is way way more wiser, if you really have cliff with lava or sharks or a mountain wall ahead of the ruway at least get Vy speed do a wingover 

Edited May 25, 2020 by Ibra

[carusoam]

So....

We get some choices...

1) Avoid the steep banks while flying at 1g...

2) When pressed into a canyon, unload the wing, while banking...

3) Keep the power up, to avoid slowing down, while banking...

4) Memorize a few points on the chart of stall speed vs. bank angle, these are for MGToW, allowing some natural buffer...

• 30° banks...
• Full flaps... and T/O flaps for this case...

5) Knowing these few points of the stall speed chart will increase your interest in knowing about...

• AOAi(s)
• G meters
• Seat of the pants sensitivity

 

6) there is something lost in the discussion...  (please add some detail)

• lowering the nose definitely decreases gs, immediately.... we just run out of time before the turn is finished... (prevent impending  stall 101, used for engine out in a climb)
• keeping the nose lowered in descent... Seems to unload the wings over a longer period of time... At constant 0.Xgs(?)
• allowing the nose to drop as trimmed, during the turn... has been known to work, by not loading the wings above 1.0g

7) Gs are naturally increasing with bank angle... it is an additional challenge to tell when adding to the gs when pulling back on the yoke...

• Some people don’t have much calibrated feelings in their extremities...
• Some people don’t re-trim the plane...
• Not re-trimming the plane can lead to constantly holding the nose up, making it difficult to recognize the additional g-load...
   

8) My stall speed charts assume 1.0gs constantly...

• how do I adjust the stall speeds for less than 1g
• how do I adjust the bank angle for less than 1g
• Do I just use this knowledge as a buffer for times when things momentarily exceed 1g?

9) As a case study for the effects of accidentally flying into a box canyon... we have...

• baseball pitching, Yankee great, Cory Lidle...
• Who flew up the East River in an SR20...
• East River runs between Manhattan and the Bronx, the home of Yankee stadium...
• with his CFI...
• In (Imaginary) tight quarters... trying to follow the proper rules of airspace...
• The plane was fully loaded with stuff at the beginning of a long X-country flight heading home to CA...
• over tightened the turn...
   

10) Technicality...

• Does the lowered nose in constant descent help avoid a stall?
• How does it help?

 

• It Keeps the plane from slowing (Very Helpful)
• much is left to the pilot... don’t over bank, don’t slow down...
• If you hear the stall horn unexpectedly... lower the nose and level the wings... while you still can...

Let me know what I missed... 

PP thoughts only, not a CFI....

Best regards,

-a-

[Andy95W]

5 hours ago, brndiar said:

 

when you are in descent, relative wind is from below, AOA rise.

Back side of the power curve, this could be a significant factor.  In normal operation, not really.