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Stall Practice Gone Wrong?

krw5927

Well Known Member
Nearing the end of my Phase 1 testing of my RV-9A, I recently began flight tests at increased weight and varying CG locations within the envelope. The plane was loaded with full fuel, one 50-lb sandbag in a duffel strapped down in the passenger seat, and one 50-lb sandbag in a duffel strapped in the baggage compartment. The weight and CG were calculated to be well under max gross and nowhere near aft limits.

I climbed to 5k (4k AGL), and determined the aircraft to have positive stability in all axes as normal. I then performed two power off stalls (one clean, one full flaps), both of which went exactly like all previous power off stalls: mild buffet followed quickly by a slight nose drop, release back pressure and the plane resumes flying. I set up to do one more clean power off stall in order to capture a data point for my Skyview AOA indicator.

This time, however, as airspeed decreased and I increased back pressure on the stick, and with eyes fixed firmly on the centered ball, instead of the usual buffet I was instantly and abruptly rotated nose down, wings level, to what I found out later from recorded EFIS data was a 64-degree nose-down pitch. My cell phone, which was sitting on the seat next to me along with the sandbag, hit the canopy. It seemed like forever before the airplane had built enough speed to recover, but thankfully it did so without any ill effects. Analyzing the data, it turns out that I lost about 600 feet altitude in recovering from this stall. The whole event lasted about 7 seconds.

What went wrong? Well, I can't say for sure but I really hope it's me and not the airplane. But to say that this event got my attention is a huge understatement - I fully expected to have pinched a hole in my seat. I'm quite apprehensive about conducting any further stall testing now, at least until I receive some additional upset training with an acro instructor in a different aircraft.

I feel that I need to continue learning how this airplane stalls at all weights and CGs for safety, but if my aircraft has some unique aerodynamic characteristic that makes it just fall out of the sky, well, I just can't accept that. I'm half tempted to enlist a professional test pilot to perform a complete stall workup.

Have others experienced such abrupt stall breaks in their RV-9's? What could I have done that caused this? Better yet, what can I do to prevent it from happening again (besides not stalling)?

All thoughts welcome. I've got thick skin, and I really hope it's pilot error.
 
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Doesn't sound like pilot error at all, especially since wings were level. I'm guessing you fully stalled the wings, whereas the previous were just partial. The RV wing breaks much more abruptly than the Cessna/Pipers. I found a little extra weight made a huge difference in the handling characteristics at the slower airspeeds.

I felt fairly proficient for the stall\spin testing until I actually started doing it. I performed the aft CG limit stalls than turned it over to a much more experienced pilot to test the vey edges of the envelope and aerobatics testing.
 
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Do you have a record of the minimum airspeed you hit at the apex (?) of the stall? I wonder if you were in a climb when the stall happened and the airplane got really slow before accelerating in a descent.
 
same story

well Kurt,
the exact same thing happened to me when I had only a couple hours stick time. Nice to hear you had the instrumentation to make some analysis of it.

... my instructor was power on, and was trying to 'hang it on the prop', which is to say, a prolonged, mushing stall, no doubt descending.
Only speculation, but seems the wing/flaps may blank the tail, and the downforce of the elevator suddenly stops.
I thought we snapped past vertical, and certainly lost a similar altitude prior to recovery. Nothing like a windshield full of nuthin' but lake, to get your attention.

I guess that's why they call these, 'experimental' aircraft, because not all corners of the envelope have published data....(much as I would like to have it!)

I also was initially surprised and a bit leery of this corner of the envelope, but suffice to say that it is an extreme condition. will it be an issue in normal ops? Probably not.
If you were constantly doing hammerheads, smoke on...etc.....you'd want to know and learn to predict, if not tame, this tiger.
but we aren't doing aero, so that's less of an issue.
If you are making the classic 'too steep' turn to final, at low speed, and low altitude, and you enter this condition, then yes......you have a problem!
 
I have had this happen on a couple of occasions. It definitely get's your attention! I didn't get quite so nose down as you described but definitely saw a significant pitch down prior to recovery.

IMO you did nothing wrong and just experienced a fully developed stall. In most cases, pilots recover closer to the onset of the stall and seldom take them that deep.
 
Do you have a record of the minimum airspeed you hit at the apex (?) of the stall? I wonder if you were in a climb when the stall happened and the airplane got really slow before accelerating in a descent.

Definitely not in a climb. As many have described, the airplane "mushes" down in a nose high attitude at a good rate of descent (450 fpm or more) when slowing to stall. Maybe that's me not being aggressive enough on the stick to hold altitude immediately prior to stall.

Perhaps the "mushing" blanks the tail somewhat?

Clean power off stalls are right about 50 kts indicated, and this one was no different. Just more violent and frightening for the unprepared.
 
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Secure your cell phone! ...and any other objects that can go flying around the cockpit. FOD, even from very small items is no good.
 
If you have the data from the Skyview, go back and see what the pitch attitude was and try to extrapolate an AOA.

Sounds to me like you may have somehow blanked the tail , and gotten a full on tail stall.
 
Looking at your location (KS) you may have flown into some windshear (updraft) just as you approached the stall. This would stall the whole wing at once, with the result you saw, as a previous post indicated.
 
I wouldn't say stall practice went wrong at all. I'm guessing from what's you've written, the reason for the drop was outside the plane (air/wind/turbulence).

But regardless, you need to be comfortable dealing with this. This is stall recovery 101. Learn it for your plane. And with my CFI hat on, don't fixate on the ball. Bring your head up and look at the horizon. Check the ball occasionally and feel the plane.

You don't need a professional test pilot. I'd recommend you get with an experienced RV pilot who will offer some help, make sure your CG is good, then go fly some stalls. Power on, power off, banked, accelerated.

You need to be in command of the plane (soon). You need to be one with the plane.

Good luck!
 
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agreed...fly the plane

Bryan is bang on here. ....
If I was age 17 again, with 20 hours, and I was out practicing spins in the little Cherokee 140, this would have been tame by comparison!
...I probably would have said "yee-haaa" as I collected the pens & junk off the dash!
Just keep doing it, at a good altitude, until you can feel it coming....

that's what makes a safe pilot, in any airplane.
 
On that note.....

Your stalls sound about right. As was noted, you probably got if fully stalled and gravity took over. Nice job of recovery.

On that note, I was not comfortable using ballast when there is a moment of negative G's at the stall onset. I contacted my DAR and asked if I could put someone in the passenger seat for full gross weight testing and to log some information. He said that would be fine, that they are essential crew. I did not abuse this permission.

We went out and did the stall and he recorded the airspeed at the stall. Mission accomplished. .7 to get everything done. Glad I didn't use ballast. I couldn't imagine something coming loose and jamming the controls.
 
Ok so it's starting to sound like I made much ado about nothing, as others have experienced the same behavior.

I really like the idea of another more experienced pilot as "ballast". Much easier to keep in the seat and not interfering with flight controls. I'm very glad I removed the passenger stick for sandbag ballast testing.

Had I had any idea that this was possible, I certainly would have secured my phone. Every piece of literature on RVs I've ever read, including the Vans website, brags about how docile stalls are. Ha.

I'm glad to hear that this is somewhat normal and to be anticipated on each deliberate stall. Obviously I need more time to get to know this aircraft. That is precisely what I believe Phase I to be. Am I done after Phase I? Certainly not.

This is also the reason I am glad to have a couple other forms of stall warning - AOA and the Vans stall vane, especially in the first couple hundred hours while this plane and I figure each other out.

I appreciate everyone's comments and advice. Keep 'em coming.
 
I have not flown the nine but on my six I would not consider that normal behavior. I have done a lot of stalls and they are all very predictable. I wonder perhaps if it might have been a bit of a accelerated stall. Stick forces get light slow with a aft CG.

George
 
I have not flown the nine but on my six I would not consider that normal behavior. I have done a lot of stalls and they are all very predictable. I wonder perhaps if it might have been a bit of a accelerated stall. Stick forces get light slow with a aft CG.

George

Exactly what I was going to post as a follow-up.
 
Exactly what I was going to post as a follow-up.

I was kinda thinking along the same lines. I wonder if, with the aircraft at slow airspeed, but just fast enough to have good elevator authority, it wouldn't be possible to rush the stall entry, causing an accelerated stall that would behave exactly as you describe, with an RV.
 
Stall vs unusual attitude

Kurt

Glad everything turned out ok for you..

Your mention of getting some acro/unusual attitude training is spot on...It will prepare you for the potential sight out the window, aircraft attitude and on how to recover and see/learn on what just happen without scaring you or braking something..

You will be able to visualize the maneuvers..

Good luck

Bruno
 
I just finished phase 1 in my 9a and I have to say with 160 lbs of salt in the pass seat, another 100 lbs in the baggage area, me (170 lbs) and full fuel the power off and power on stalls in level flight were all a buffet followed by a slight nose drop, speed increase, nose climb and repeat. I tried more force pulling back on the stick to force an abrupt stall but the rocking up and down with the nose continued so I terminated. I thought man this rocking motion would get anyone's attention. Only in a banking stall could I get an abrupt nose drop where a release on the stick back pressure was required.

Now all bets are off if there is wind shear, gusts, etc. Requires you to be on your game.

Jim
Rv9a
 
Glad I didn't use ballast. I couldn't imagine something coming loose and jamming the controls.
We did the exact same thing for the same reason.

Clean power off stalls are right about 50 kts indicated, and this one was no different. Just more violent and frightening for the unprepared.
Seems a little fast :confused:
I'd expect it to be between 40-45 kts.
 
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Hi Kurt,


You might give Mike Seager a call and discuss with him. In transition training I was doing power on stalls like a Cessna and he cautioned me to throttle back like a landing configuration. And this was a 7 not a 9. The power on can be quite dramatic, apparently, because of the high power of the RV's.

We did some high power slow flight and the nose was in the sky! Awesome!

He also cautioned me to keep the nose low after take off where I could see the horizon as it climbs so rapidly that a stall there would be, well, bad.

I am certainly no expert, but I am sure Mike would welcome your call and discussion.

Great you are flying, hope to join you in phase I this year.
 
...Sounds to me like you may have somehow blanked the tail , and gotten a full on tail stall.

I think you are right on. I was demonstrating "falling leaf" to a friend when after the 5th or 6th stall the "bottom dropped out" and a significant nose low was necessary for recovery. My thought was tail-stall.

Those that have stalled an out-of-rig Cessna with a student pilot at the controls know the excitement of a not-so-benign stall. We can get spoiled by the stalls in the RV's, but sometimes they can fully develop and really get your attention. Just a reminder to everyone to practice stalls occasionally. Not just one or two, but 10 or 20. Take em deep!
 
Phase II

Keep doing your air work with various weights and take an experienced pilot after phase I with you to see if you can duplicate this event.
After phase I, we loaded up the two of us, full fuel and nearly 50 lbs in the baggage area to get to max weight then we went up and did air work just like we did in phase I. There is a difference in characteristics at max than with just a single pilot. It was a great exercise.
Flying with Mike Seager, we were doing full power steep climbing turns to a stall. That first one got my attention in a hurry as I hesitated to pull the power as I rolled the wings level and it goes down hill in a hurry in that configuration.
He made sure that I learned my lesson and made me do several more in each direction. I learned a lot from Mike.
Stay safe.
Pat Garboden
Katy, TX
RV9A N942PT
 
In over 300 hours, and countless stalls, I have only had this happen in turbulence, never in smooth air. My guess is a gust or some turbulence. That is for power-off. Power on, I can't really get a stall unless I am pretty far aft on the CG, or do an accelerated stall. Solo, with full power and full aft stick, I can drop to 0 indicated airspeed and show about 500fpm climb. That takes really heavy right rudder, and if the ball is out of center, all bets are off. It can get ugly real fast. 700 feet loss does sound like a lot, however. Reaction time and practice should bring that to a more reasonable number, regardless of conditions. Stick with it...

Bob
 
This time, however, as airspeed decreased and I increased back pressure on the stick, and with eyes fixed firmly on the centered ball, instead of the usual buffet I was instantly and abruptly rotated nose down, wings level, to what I found out later from recorded EFIS data was a 64-degree nose-down pitch.

Not being in the aircraft with you, it's impossible to tell for sure, but I think these two actions may be the key: eyes inside the cockpit and moving the stick rearwards at the stall. It sounds like you may have induced a low speed accelerated stall with somewhat more abrupt stall characteristics than a typical 1 G stall. The rearward stick movement could have been accompanied by an upward pitch moment which you may not have noticed as you concentrated on the ball.

Since you experienced negative G's in the pitch down, you were probably no longer stalled in the classic sense since your wings were providing negative lift. That sounds like a greater than normal push forward on the stick during recovery.

All this is speculation, but, if true, indicates that there is probably nothing wrong with your airplane.

-John
 
SNIP

Since you experienced negative G's in the pitch down, you were probably no longer stalled in the classic sense since your wings were providing negative lift. That sounds like a greater than normal push forward on the stick during recovery.

SNIP

-John

This seems correct - the only way the cell phone hits the canopy is if the wings are generating lift at a negative angle of attack. I suppose the rotational velocity of the aircraft pitching over could contribute, but... Seems like a little too much forward stick during the recovery.
 
Thanks all for the comments. After I get some upset recovery training from an experienced acro instructor, I'll resume stall testing. Planning to do a BUNCH of them to get comfortable and learn this airplane.
 
After I get some upset recovery training from an experienced acro instructor, I'll resume stall testing.

Smart.

I am currently doing phase 1 testing of my Rocket, did power on stalls (including full power) the other day. The aerobatic training and continued practice in my Decathlon keeps the adrenaline at reasonable levels.
 
just another observation

... Seems like a little too much forward stick during the recovery.

I think this is a great thread.....we should always be talking about things that effect safety.
I am making the assumption that Kurts stall was very similar to mine, and there was no 'forward stick'.
When it stalls, and snaps to extreme nose-down, it's in .01 seconds.
the stick is still in your lap.
My main interest is .......how much stall 'training' is it prudent to do from these unusual attitudes, with a ship that is only stressed for +4.4/-1.75 G at under 1600 lb.!?!??
I believe my G-meter showed more than -1.75, and I did a thorough inspection upon return to the field, you can be sure of that!
.....but what if it shows -2.5? is the aircraft a write-off?
 
Thanks all for the comments. After I get some upset recovery training from an experienced acro instructor, I'll resume stall testing. Planning to do a BUNCH of them to get comfortable and learn this airplane.

Kurt, that is not necessary. There is nothing wrong with how your airplane stalled. Just be prepared that while normally the stall characteristic of your RV is generally benign, it can however be more significant under the right circumstances. That is why you should practice them at altitude.

Upset recovery training is NOT necessary for stall training/practice. It would be a wrong assumption that it is. In fact, anyone who would suggest a pilot get upset recovery training prior to practicing stalls is mistaken. That idea produces a completely unnecessary and uneasy feeling about stalls which I adamantly reject as misleading.
 
Upset recovery training is NOT necessary for stall training/practice. It would be a wrong assumption that it is. In fact, anyone who would suggest a pilot get upset recovery training prior to practicing stalls is mistaken.

Agree totally with the above when performing stalls in a thoroughly tested aircraft.

However when testing a new experimental aircraft, particularly at the edges of the envelope, I believe upset training is a huge benefit to the test pilot.
 
Kurt, that is not necessary. There is nothing wrong with how your airplane stalled. Just be prepared that while normally the stall characteristic of your RV is generally benign, it can however be more significant under the right circumstances. That is why you should practice them at altitude.

Upset recovery training is NOT necessary for stall training/practice. It would be a wrong assumption that it is. In fact, anyone who would suggest a pilot get upset recovery training prior to practicing stalls is mistaken. That idea produces a completely unnecessary and uneasy feeling about stalls which I adamantly reject as misleading.

I respect your point, Tony, but for myself I also disagree with it. I am not as experienced a pilot as you or many others on this forum, and I also readily admit that I can, have, and will, screw up. If I screw up and find myself in an incipient spin, I'd sure like to more instinctively be able to correct the problem rather than burning altitude thinking about it. For me, this means practice in a known (and approved) airplane with an experienced instructor.

Many private pilots have no practical experience with spin recovery. We're taught the book basics of recognition and recovery, but many of us never get the chance to practice it.
 
I have not flown the nine but on my six I would not consider that normal behavior. I have done a lot of stalls and they are all very predictable. I wonder perhaps if it might have been a bit of a accelerated stall. Stick forces get light slow with a aft CG.

George

Exactly what I was going to post as a follow-up.

I was kinda thinking along the same lines. I wonder if, with the aircraft at slow airspeed, but just fast enough to have good elevator authority, it wouldn't be possible to rush the stall entry, causing an accelerated stall that would behave exactly as you describe, with an RV.
These are my thoughts in reading this thread as well. I have experienced an accelerated right turning stall with an instructor who I let fly the 9 for the first time. He was a competent instructor but had never flown any RV before. He was flying the airplane and doing a power on turning stall when out of the blue the right wing fell (in a right turn). To say I was surprised would be a great understatement! I had my hand on the wind screen brace and fighting the urge to grab the stick while staring at the ground fill up the windscreen. I believe you may have experienced an accelerated stall as the others have commented.
 
Upset Training

Many years ago a VERY Heavy student and a CFI in a near new Cherokee 140 doing stalls: As airplane stalled, student stomped on rudder, airplane rolled on its back and started a split S. High airspeed and high G on recovery. Pilots seat broke and the rivets on the top of the wings had dime sized circles where paint came off. No other damage.
I was in a two seat high performance aerobatic airplane with an aviation writer who will remain unnamed: clearing turn, a bit too aggressive on the back pressure, from a steep bank to the left we snap rolled almost 1 1/4 turns to upright. The writer said what the XXXX was that, he didn't have a clue what he did.
So yes, upset training is directly related to stalls and spins.
 
Stalls

One thing that has not been mentioned regarding the OP is the possibility of excessive elevator travel. Even a couple of degrees of extra travel has the potential to adversely affect the stall on some airplanes.
The more likely scenario with the OP is that the airplane was sinking significantly, he was focused inside the airplane, got a bit aggressive on the back pressure and induced an accelerated stall, then overcorrected with forward stick held too long.
 
My observations, while conducting either BFR's, or Unusual Attitude (Upset) training, is that almost everyone over-reacts to a stall.

Way too much forward stick, nose 30 degrees below the horizon at about 0.3G, then haul back on the stick and come close to or actually get into a secondary stall. :(

By the end of the session, they can stop a stall with minimal nose down attitude change, and never approach a secondary (accelerated) stall. Lose maybe 50' altitude. :)

It's all in the angle-of-attack.
 
Re-reading your original post... "This time, however, as airspeed decreased and I increased back pressure on the stick, and with eyes fixed firmly on the centered ball, instead of the usual buffet I was instantly and abruptly rotated nose down, wings level, to what I found out later from recorded EFIS data was a 64-degree nose-down pitch.

That is actually one way you do an "accelerated stall".. increasing back pressure while airspeed is decreasing.

Makes no difference though. As you said, your "eyes fixed firmly on the centered ball". With your "ball" centered you are not going to spin and a nose low pitch attitude is not out of the ordinary. You had already said that you had done several stalls and all was normal. That tells me you did not install one wing upside down or reverse your elevator controls. Your -9 is like the hundreds of others out there.

I am certainly not opposed to "upset training". I have done it. Didn't care for it. Did it help me with stalls..absolutely not. Am I a better pilot for it...No. What does make me a better pilot is using solid technique. I would HIGHLY recommend you take a few minutes and review the FAA's Airplane Flying Handbook. IMO the best flight instruction money can buy (It's free).
 
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