Another Fatal Vmc Demo Stall Spin

[MountainDude]

 

[dtuuri]

I'd like to think the pilot was simply trying to transmit the reason they were crashing and not, as Brown assumes, asking for help. That would be a heroic action that could help investigators. Maybe it's why nobody in this thread is speculating as to the cause — we already know.

 

[rangerz]

Unfortunately, light twin on a VMC training mission that crashes isn't really going to stump investigators. These have been pervasive since the invention of light twins and ME rating requirements for VMC demonstrations.

One of my college profs was killed as a student in Baron VMC training gone bad back in the early 2000's. Flat spin from 8000' into a corn field.

Once could argue in the past, there wasn't another option than live filght -- with simulators today it sure seems like we could find another way to handle this part of ME training and stop expecting low time pilots AND low time instructors to consistently put their lives in danger. Even experienced MEIs and DPEs have lost their lives as you're operating at the edge of the envelope where small mistakes by the student can override the best skills available.

 

[MountainDude]

Unfortunately, light twin on a VMC training mission that crashes isn't really going to stump investigators. These have been pervasive since the invention of light twins and ME rating requirements for VMC demonstrations.

One of my college profs was killed as a student in Baron VMC training gone bad back in the early 2000's. Flat spin from 8000' into a corn field.

Once could argue in the past, there wasn't another option than live filght -- with simulators today it sure seems like we could find another way to handle this part of ME training and stop expecting low time pilots AND low time instructors to consistently put their lives in danger. Even experienced MEIs and DPEs have lost their lives as you're operating at the edge of the envelope where small mistakes by the student can override the best skills available.

Well said. That's what airlines do.

 

[Fearless Tower]

I'd like to think the pilot was simply trying to transmit the reason they were crashing and not, as Brown assumes, asking for help. That would be a heroic action that could help investigators. Maybe it's why nobody in this thread is speculating as to the cause — we already know.

Id agree with you. I think Juan is trying to use this to further his crusade, nothing else.

But Juan is no stranger to stretching the details....

 

[hindsight2020]

We deal with these type of reactions in .mil primary training: It's called improper reaction to stress/stressor. From an instructor cadre perspective, it's an important aspect of instructional competence to be able to identify in order to catch in time, before we become a hole in the ground.

Prioritizing comms, irrationally but calmly, while otherwise locking up and/or misapplying the necessary control inputs to recover the aircraft, is a common one. It's a startled reflex, it just doesn't sound like one. Again, seen it too many times, especially during my days working in primary training (T-6 II). Lots of control input freeze/lock-ups, while talking to you or trying to finish a radio call to ATC casually. If you asked them on the spot what's going on, they'd calmly tell you, or hell even ATC (PTT still smashed in a kung fu grip). Channelization is a perplexing dynamic indeed.

Lastly, lionizing pilot error causals under the consolatory rebranding of heroics just because some are uncomfortable with the notion that people died of their mistakes, doesn't do those attempting to learn from it one damn bit of good. I mean this with respect, but if I had a quarter for every time I've heard "withheld/delayed ejection to save innocents on the ground" from the grieving survivors and the media, I'd be retired by now. Safety investigation shows otherwise. Some choose to lie to the families because we as collective want to spare them the pain. And that's a very human response indeed, but there's no place for that emotional placebo in aviation safety circles. Too hot? get out of the kitchen.

As to the youboobers, their motivations or lack thereof, keep my commentary out of it. My post has zero to do with that cult of personality kerfuffle.

 

[3393RP]

I'd like to think the pilot was simply trying to transmit the reason they were crashing and not, as Brown assumes, asking for help. That would be a heroic action that could help investigators. Maybe it's why nobody in this thread is speculating as to the cause — we already know.

Prioritizing comms, irrationally but calmly, while otherwise locking up and/or misapplying the necessary control inputs to recover the aircraft, is a common one. It's a startled reflex, it just doesn't sound like one. Again, seen it too many times, especially during my days working in primary training (T-6 II). Lots of control input freeze/lock-ups, while talking to you or trying to finish a radio call to ATC casually.

Lastly, lionizing pilot error causals under the consolatory rebranding of heroics just because some are uncomfortable with the notion that people died of their mistakes, doesn't do those attempting to learn from it one damn bit of good. I mean this with respect, but if I had a quarter for every time I've heard "withheld/delayed ejection to save innocents on the ground" from the grieving survivors and the media

My take:

The person was speaking in complete terror and helplessness. He repeated the phrasing in a second transmission, with the same rapidity and obvious panic.

It had nothing to do with informing the world of the situation.

One occupant was flying under an eight month old Basic Med issuance and an ASEL certificate. The other occupant is not in the FAA pilot database.

 

[TrueCourse]

I remember on my CMEL ride how my examiner was encouraging me to push the VMC demo further than I was, but even he was a little apprehensive about it. And, it was only a PA44! I never enjoyed the low speed regime in the twin during training and it was one reason (lack of training funds was the other) that I didn’t aim for the MEI when I became an instructor.

The irony of dying while demonstrating how to avoid dying is sobering.

 

[MauleSkinner]

Unfortunately, light twin on a VMC training mission that crashes isn't really going to stump investigators. These have been pervasive since the invention of light twins and ME rating requirements for VMC demonstrations.

One of my college profs was killed as a student in Baron VMC training gone bad back in the early 2000's. Flat spin from 8000' into a corn field.

Once could argue in the past, there wasn't another option than live filght -- with simulators today it sure seems like we could find another way to handle this part of ME training and stop expecting low time pilots AND low time instructors to consistently put their lives in danger. Even experienced MEIs and DPEs have lost their lives as you're operating at the edge of the envelope where small mistakes by the student can override the best skills available.

I see no reason for Vmc demos, either in airplanes or simulators. Most of the time they’re done in airplanes designed to have benign flight characteristics in that flight regime, contrary to the twins that most people will fly in “real life”. A competent instructor could teach the proper response in a Citabria…opposite rudder, reduce thrust, lower the nose. Basically we’re teaching incipient spin recoveries in an airplane that’s not certified for spins, and is unlikely to recover if a spin is entered. The overwhelming majority of pilots I’ve seen get to that point in a sim actually increased thrust on the good engine and pulled back on the stick.

They’re also not trained to what I would consider any level of real proficiency…just enough to pass the checkride. Obviously the training doesn’t have the desired effect.

Much like the way we trained stalls in jets for years…”power out of the stall, there’s no need to lose altitude.”After a handful of high-profile stall accidents, the FAA finally realized that maintaining back pressure on the stick for a maximum 100’ of altitude loss in a stall recovery in a jet was counterproductive.

 

[Rockymountain]

I felt like the Vmc demo taught me a lot about flying, even flying singles. Did mine in a turbocharged twin at altitude, which obviously takes a little more care. But the lesson learned in asymetric thrust, AoA and power management is stick and rudder skills that translates to most flying. If you have students too green to safely do it, and instructors with too little experience, or too permissive in letting things go too far, or too skimpy in preflight education, can be a problem. But that is true of all flight training. The engine related accident rate of light twins tells us that we are certainly not overtraining light twin pilots, and they do regularly forget about Vmc demos in the real world.

 

[Tokirbymd]

Unfortunately, light twin on a VMC training mission that crashes isn't really going to stump investigators. These have been pervasive since the invention of light twins and ME rating requirements for VMC demonstrations.

One of my college profs was killed as a student in Baron VMC training gone bad back in the early 2000's. Flat spin from 8000' into a corn field.

Once could argue in the past, there wasn't another option than live filght -- with simulators today it sure seems like we could find another way to handle this part of ME training and stop expecting low time pilots AND low time instructors to consistently put their lives in danger. Even experienced MEIs and DPEs have lost their lives as you're operating at the edge of the envelope where small mistakes by the student can override the best skills available.

Totally agree on using sims to train this. But would require every MEI/Flight School to have access to one, and revamping of the DPE checkride to involve both in flight and sim evaluation. I have a pretty extensive home sim setup and parameters that match my Seneca so I can train these events. But to make one "certified" would be prohibitively expensive.

 

[Tokirbymd]

Unfortunately, light twin on a VMC training mission that crashes isn't really going to stump investigators. These have been pervasive since the invention of light twins and ME rating requirements for VMC demonstrations.

One of my college profs was killed as a student in Baron VMC training gone bad back in the early 2000's. Flat spin from 8000' into a corn field.

Once could argue in the past, there wasn't another option than live filght -- with simulators today it sure seems like we could find another way to handle this part of ME training and stop expecting low time pilots AND low time instructors to consistently put their lives in danger. Even experienced MEIs and DPEs have lost their lives as you're operating at the edge of the envelope where small mistakes by the student can override the best skills available.

One additional point- the flight school he was chief pilot at actually has a certified Sim so you could theoretically do ground Vmc training- although I don't think it would be loggable towards the rating.

 

[hindsight2020]

Totally agree on using sims to train this. But would require every MEI/Flight School to have access to one, and revamping of the DPE checkride to involve both in flight and sim evaluation. I have a pretty extensive home sim setup and parameters that match my Seneca so I can train these events. But to make one "certified" would be prohibitively expensive.

This is all blood diamonds for the airlines; the tacitly complicit and entitled flying public actually, if you really want to get to the bottom of it.

 

[FlyingTiger]

Totally agree on using sims to train this. But would require every MEI/Flight School to have access to one, and revamping of the DPE checkride to involve both in flight and sim evaluation. I have a pretty extensive home sim setup and parameters that match my Seneca so I can train these events. But to make one "certified" would be prohibitively expensive.

Possible solution may be to require an endorsement prior to the checkride similar to spin training for CFIs.

That would eliminate the need for every flight school to have the appropriate simulator and for it to be addressed as part of the checkride.

 

[dtuuri]

I'm wondering about the wisdom of "blocking" the rudder pedals by the CFI/DPE. I get it that would raise VMC allowing a bigger margin above the stall, but would you want somebody interfering with your controls while your plane approaches a stall with full asymmetric thrust?

And... what about the non-critical engine? Would CFIs start VMC training with a student by having them demonstrate the non-critical engine first? The logic being: less asymmetrical thrust would be safer for a beginner, but neglecting that the lower VMC would be closer to the stall?

And, why the push by the FAA and airlines for multiengine experience in the first place? There's little correlation between a Part 23 light twin which aspiring airline pilots can barely afford and a Part 25 transport category airplane. Once you're hired, you have to forget everything you thought you needed to know about multiengine operations and learn a whole new language rooted in guaranteed takeoff performance after the loss of an engine during takeoff. The irony is that about the only thing that does correlate is, wait for it... VMC training. You don't get that with multiengine hours in your logbook, you get it prepping for your multi flight test. So, once you have, say, 10 hours of multi training, there's nothing more to be gained except negative transfers with respect to operating multiengine airplanes in an air carrier environment.

 

[MauleSkinner]

The irony is that about the only thing that does correlate is, wait for it... VMC training.

Except that the “guaranteed performance” part of the equation further emphasizes that we never fly near Vmc. If and when a loss of control occurs, either two pilots are so far out of the loop that recovery is highly unlikely, or a mechanical condition exists that changes the aerodynamics of the airplane such that loss of control is nowhere near Vmc.

 

[dtuuri]

Except that the “guaranteed performance” part of the equation further emphasizes that we never fly near Vmc. If and when a loss of control occurs, either two pilots are so far out of the loop that recovery is highly unlikely, or a mechanical condition exists that changes the aerodynamics of the airplane such that loss of control is nowhere near Vmc.

Agreed. But the lesson to be learned is simply that multiengine planes fly the same as singles when either both engines are operating or neither are. You have to react to cut the power and lower the nose the instant you run out of rudder. There was a crash of a Convair, IIRC at Kalamazoo, where the rudder rigging due to stretched cables caused VMC to be high enough that control couldn't be maintained at specified speeds. So, there needs to be enough training, just like stall recovery, to react correctly and fast, imo, but not an hour more.

 

[MauleSkinner]

Agreed. But the lesson to be learned is simply that multiengine planes fly the same as singles when either both engines are operating or neither are. You have to react to cut the power and lower the nose the instant you run out of rudder. There was a crash of a Convair, IIRC at Kalamazoo, where the rudder rigging due to stretched cables caused VMC to be high enough that control couldn't be maintained at specified speeds. So, there needs to be enough training, just like stall recovery, to react correctly and fast, imo, but not an hour more.

i would still suggest, however, that a Citabria would be just as good a platform for the training as a multi engine airplane or simulator.

It’s the reaction to the airplane motion that critical. Much like unusual attitudes, where I frequently see people do it correctly when we do unusual attitude training, but when they find themselves in an actual unusual attitude, they do something entirely different.

 

[midwestpa24]

I'm wondering about the wisdom of "blocking" the rudder pedals by the CFI/DPE. I get it that would raise VMC allowing a bigger margin above the stall, but would you want somebody interfering with your controls while your plane approaches a stall with full asymmetric thrust?

And... what about the non-critical engine? Would CFIs start VMC training with a student by having them demonstrate the non-critical engine first? The logic being: less asymmetrical thrust would be safer for a beginner, but neglecting that the lower VMC would be closer to the stall?

And, why the push by the FAA and airlines for multiengine experience in the first place? There's little correlation between a Part 23 light twin which aspiring airline pilots can barely afford and a Part 25 transport category airplane. Once you're hired, you have to forget everything you thought you needed to know about multiengine operations and learn a whole new language rooted in guaranteed takeoff performance after the loss of an engine during takeoff. The irony is that about the only thing that does correlate is, wait for it... VMC training. You don't get that with multiengine hours in your logbook, you get it prepping for your multi flight test. So, once you have, say, 10 hours of multi training, there's nothing more to be gained except negative transfers with respect to operating multiengine airplanes in an air carrier environment.

The whole idea with blocking the rudder to simulate VMC is to keep the aircraft well beyond stall. The CFI/DPE should clearly communicate what they are doing, and all they are doing is using their foot to keep the student from having all of the available rudder. All we were looking for was the airplane to start to yaw and not having enough rudder to compensate, but at much higher speeds that actual VMC. Once you start to see that yaw you take corrective action, which is the point of VMC training. As soon as you run out of rudder, pitch down, reduce power on the good engine, and get the airplane straightened out.

 

[PaulS]

Ok, I need some help understanding this. Blocking the rudder, what are you doing, preventing movement of the rudder so the student thinks he's at the end of travel and reacts? Proper reaction for a spin, PARE Power to idle, ailerons neutral (that's a little counter intuitive, but essential), Rudder opposite dropped wing aggressively, elevator push to unstall wing. Preferably the last three simultaneously. Is this the right reaction? I had my first flight in a twin, first landing. But I had to stop to a later date as I'm getting a new to me plane I have to check out in.

 

[dtuuri]

Ok, I need some help understanding this. Blocking the rudder, what are you doing, preventing movement of the rudder so the student thinks he's at the end of travel and reacts?

Yes, that's the theory, but I don't want anybody restricting MY controls. S'pose the thing stalls for some unexpected reason at a higher airspeed than anticipated. S'pose the DPE/CFI also has control of the throttles because he's a control freak? I'd be the first to feel the loss of control and the last to be able to correct for it. Not for me, thanks. Please keep your boots and mitts to yourself, CFI.

 

[Mikey52]

Yes, that's the theory, but I don't want anybody restricting MY controls. S'pose the thing stalls for some unexpected reason at a higher airspeed than anticipated. S'pose the DPE/CFI also has control of the throttles because he's a control freak? I'd be the first to feel the loss of control and the last to be able to correct for it. Not for me, thanks. Please keep your boots and mitts to yourself, CFI.

So you would rather spin the twin, versus completing the vmc demo more safely?

 

[midwestpa24]

Ok, I need some help understanding this. Blocking the rudder, what are you doing, preventing movement of the rudder so the student thinks he's at the end of travel and reacts? Proper reaction for a spin, PARE Power to idle, ailerons neutral (that's a little counter intuitive, but essential), Rudder opposite dropped wing aggressively, elevator push to unstall wing. Preferably the last three simultaneously. Is this the right reaction? I had my first flight in a twin, first landing. But I had to stop to a later date as I'm getting a new to me plane I have to check out in.

It is not a stall recovery. VMC is where you no longer have enough rudder authority to overcome the power of the good engine. The aircraft starts to yaw towards the dead engine and you don't have enough airflow over the rudder to compensate. To recovery, reduce pitch to gain airspeed, and reduce power on the good engine to remove the adverse yaw. By blocking the rudder, you artificially lose rudder authority well over and above both VMC and stall speed. I don't understand the fear of the CFI/examiner "restricting" your controls, when it is planned for, communicated, and keeps you from getting into the extreme situation. For example, if stall is 65 knots, VMC is 70 kts, by blocking the rudder you lose yaw authority at 100+kts. It is just to simulate that lose of rudder authority.

Where VMC demos are dangerous is when you are slow enough and the vertical tail stalls (yes the vertical tail has a critical AOA too!). You suddenly lose all yaw authority and the airplane snap rolls. Combine that with being at or near stall speed, and you are now in a spin.

 

[dtuuri]

So you would rather spin the twin, versus completing the vmc demo more safely?

I would rather NOT spin — that's why I want MY hands and feet on the controls and nobody else's.

 

[midwestpa24]

I would rather NOT spin — that's why I want MY hands and feet on the controls and nobody else's.

Just a question, do you have your multi or done multi training?

 

[dtuuri]

Just a question, do you have your multi or done multi training?

Gosh yes, but not a lot of multi training. I have been through sim training at FSI for a Cessna 421 and owned a PA-30 for a while. I wrote my own 135 LOC and then took an FAA check ride in that Twinkie. An FAR 135 check ride in a PA-31P Navajo in the '70s and I flew a Turbo Commander for a couple years in the early '80s. My own ME flight test was in an Apache and my ATP was in a PA30 at Burnside-Ott at Opa-Locka nearly 50 years ago. Plenty of relevant experience, but not a lot giving ME dual, admittedly. Does that change my wish to not have to approach VMCa near a stall with my best foot tied behind my back? Nah.

 

[midwestpa24]

Gosh yes, but not a lot of multi training. I have been through sim training at FSI for a Cessna 421 and owned a PA-30 for a while. I wrote my own 135 LOC and then took an FAA check ride in that Twinkie. An FAR 135 check ride in a PA-31P Navajo in the '70s and I flew a Turbo Commander for a couple years in the early '80s. My own ME flight test was in an Apache and my ATP was in a PA30 at Burnside-Ott at Opa-Locka nearly 50 years ago. Plenty of relevant experience, but not a lot giving ME dual, admittedly. Does that change my wish to not have to approach VMCa near a stall with my best foot tied behind my back? Nah.

Ok, never quite sure on the internet the personal experience level of someone else. While I understand your stance, I will respectfully disagree. My opinion is that a CFI/DPE using their foot to limit rudder travel during a VMC demo is safer than intentionally taking a twin below VMC while single engine. I feel confident the safety statistics will back that up.

 

[Hengelo]

This is all blood diamonds for the airlines; the tacitly complicit and entitled flying public actually, if you really want to get to the bottom of it.

Probably the most succinct summary to date.
Personally if I never hear an "about to be dead" radio call again it will be too soon. Absolutely hate those.

 

[bbchien]

FYI dturri was a D.P.E.
yeah, let's practice bleeding!
Can we also practice (for real dead enginge) autorotation, too?

 

[Roger Wilco]

I very rarely watch amateur accident-investigator videos but the fact that the accident aircraft was a Travel Air sparked my interest. Shortly before I began working toward my MEL rating, a local aviation luminary who was highly-experienced and well-respected, perished while giving a checkride in a Travel Air. The circumstances of that tragedy were very similar to those presented in this video. Those circumstances, the timing of that accident, and the close-to-homeness made profound and lasting impressions on me: if it could happen to that guy, it could happen to me; and beware of the Travel Air.

Some years later, I took a Learjet ride with an FAA examiner who had recently survived a disastrous accident while observing another Lear checkride for a 135 operator. The applicant, in the left seat, misapplied the controls during a V1 cut and the company check airman (if I may use that term) in the right seat did not react quickly enough to recover. The applicant was killed, the check airman critically* injured, and the examiner survived with moderate injuries and a forever-altered perspective on the training of engine-out procedures. Not long before that accident, a HS125 crashed during a simulated engine failure during takeoff resulting in two fatalities. Again, the evaluator failed to recover from a misapplication of the controls. Maybe those two check airmen should not have kept their boots and mitts off of THE controls until it was too late to save the day.

Those examples, along with the far-too-many other multi-engine training accidents that have occurred, suggest the following conclusions:

​

Simulators save lives.​

​

No one is too good to screw-up, at the worst possible moment.​

​

I don't know about you, but if I'm in an an actual aircraft, pitting my human fallibility against the immutable laws of physics and the fickle finger of fate, I hope that a CFI or evaluator or any competent pilot with access to THE controls will exercise due vigilance and have the presence of mind to intervene as necessary to keep us both from becoming the subject of yet another YT accident video.​

​

Beware the Travel Air.​

While this thread raises other issues regarding ME training, those merit their own threads and have probably been discussed at length elsewhere on PoA.



*Reminds me to remind myself that the term critical engine is applicable to design and certification only, and has no operational significance to pilots.

 

[kaiser]

Wow.

I was trying to remember how I was trained, especially since today marks the 1 year anniversary of my multi ride. IIRC the DA42 we flew a was very light (like 20% under max gross), fwd CG via ballast, and in the Vmc demo took it to the stall horn. I think we always got the horn few knots under redline.

 

[MauleSkinner]

Wow.

I was trying to remember how I was trained, especially since today marks the 1 year anniversary of my multi ride. IIRC the DA42 we flew a was very light (like 20% under max gross), fwd CG via ballast, and in the Vmc demo took it to the stall horn. I think we always got the horn few knots under redline.

But the horn should be several knots above the stall.

 

[dtuuri]

My opinion is that a CFI/DPE using their foot to limit rudder travel during a VMC demo is safer than intentionally taking a twin below VMC while single engine.

How do you define VMC? loss of control? I agree intentionally going below that is unsafe. Going below the red mark on the ASI? Well, you might need to for an effective demo. The FAA says if you "need" to block the rudder because VMC is below stall, do it at least 20 Kts above the stall speed: https://www.faa.gov/sites/faa.gov/f...ion/airplane_handbook/14_afh_ch13.pdf#page=26

Slower than that, if the CFI is holding strong rudder pressure against the student's attempt to hold a heading as control is quickly (as assessed by the student who is the one on the controls) being lost and a stall is suddenly encountered — the CFI and asymmetrical thrust are both working toward a spin. What if the student reacts by just letting go?

 

[midwestpa24]

How do you define VMC? loss of control? I agree intentionally going below that is unsafe. Going below the red mark on the ASI? Well, you might need to for an effective demo. The FAA says if you "need" to block the rudder because VMC is below stall, do it at least 20 Kts above the stall speed: https://www.faa.gov/sites/faa.gov/f...ion/airplane_handbook/14_afh_ch13.pdf#page=26

Slower than that, if the CFI is holding strong rudder pressure against the student's attempt to hold a heading as control is quickly (as assessed by the student who is the one on the controls) being lost and a stall is suddenly encountered — the CFI and asymmetrical thrust are both working toward a spin. What if the student reacts by just letting go?

No offense, but I think you are missing the point of blocking the rudder. The purpose is to artificially increase VMC well over and above the airframe's VMC and stall speed by limiting the rudder authority. Honestly you could prevent any rudder authority towards the good engine and simulate this at cruise speed for what its worth. The student can see and feel what it is like to not be able to overcome the yaw from the good engine while still in a safe control range and speed. All you need to see is to recognize the loss of yaw control over the good engine, and practice the proper response. There is zero risk of a VMC rollover, stall, or spin, because you are well over the stall and VMC speed.

 

[dtuuri]

To be clear, I was "wondering about the wisdom" of blocking the rudder and musing about it from the standpoint of me being the one tested. Putting on the hat of a CFI, I'd probably back up the student with my foot in position to help if needed, not block, except in the case described by the FAA in the preceding post. But the main thing would be instructing the student to have one hand poised for an immediate retrieval of the throttle to halfway the moment the nose starts to yaw (or all the way if things really go south) and the other to move the yoke forward. My hands would be backing the student there too. Ultimately, of course, everybody has to do what they think is safest after weighing all the available information.

 

[MauleSkinner]

No offense, but I think you are missing the point of blocking the rudder. The purpose is to artificially increase VMC well over and above the airframe's VMC and stall speed by limiting the rudder authority. Honestly you could prevent any rudder authority towards the good engine and simulate this at cruise speed for what its worth. The student can see and feel what it is like to not be able to overcome the yaw from the good engine while still in a safe control range and speed. All you need to see is to recognize the loss of yaw control over the good engine, and practice the proper response. There is zero risk of a VMC rollover, stall, or spin, because you are well over the stall and VMC speed.

I think the risk is still definitely greater than zero for rollover, stall, or spin. the fact that you’re above Vmc is irrelevant, as the rudder pedal blocking effectively increases Vmc. The loss of yaw control with a blocked rudder pedal is still a loss of directional control that can lead to rollover and worse. All you need is a ham-fisted student and/or an instructor who gets his foot wedged under the rudder pedal being blocked, and you’re easily into rollover/stall/spin territory.

 

[Mikey52]

If you're flying right at stall speed + 1, any gust or turbulence can induce a stall. That is why there is usually some additive that decreases the probability of developing into a stall on approach. If doing a vmc demo, would not an increase in margin make for a safer demonstration.

Would you fly an approach in to a wind of 5 gusting to 15 at stall speed + 1? Why demonstrate a minimum controllable airspeed at vmca and not vmca+5 when stall speed could be close to vmca?

 

[dtuuri]

If doing a vmc demo, would not an increase in margin make for a safer demonstration.

Of course. That's why you shouldn't do them in a normally aspirated twin at 8000'. Unless I overlooked it, nobody opining so far has mentioned that specifically as a possible root cause. Up there, actual VMC may be below stall and you may reap the whirlwind, so to speak.

 

[Tokirbymd]

Of course. That's why you shouldn't do them in a normally aspirated twin at 8000'. Unless I overlooked it, nobody opining so far has mentioned that specifically as a possible root cause. Up there, actual VMC may be below stall and you may reap the whirlwind, so to speak.

Good point and I wondered as well. They were at 6000 AGL (6500 MSL). Not a particularly hot day but maybe conditions with stall above Vmc. But can't rule out one engine stumbling during power on stall recovery as cause as well. The student was a large man, the MEI was very slight so may have also been a situation where the student overpowered the MEI, however brief, to enter the spin condition. As I understand it, unless you extend gear and yaw back and forth significantly, the Beech won't recover from a spin. I do wonder about Juan's comment that power on the dead engine to counter the spin causing it to flatten. I get that in a single, but I would like to see data for that in a twin as its counterintuitive.

 

[dtuuri]

Good point and I wondered as well. They were at 6000 AGL (6500 MSL). Not a particularly hot day but maybe conditions with stall above Vmc. But can't rule out one engine stumbling during power on stall recovery as cause as well. The student was a large man, the MEI was very slight so may have also been a situation where the student overpowered the MEI, however brief, to enter the spin condition. As I understand it, unless you extend gear and yaw back and forth significantly, the Beech won't recover from a spin. I do wonder about Juan's comment that power on the dead engine to counter the spin causing it to flatten. I get that in a single, but I would like to see data for that in a twin as its counterintuitive.

I wouldn't be adding any thrust at all until the airflow is back to normal and the wings are unstalled. I'd be pretty aware of any secondary stalls during the dive recovery, too, and wouldn't be adding power while pointed toward the ground. That's me. I'd try to avoid being a test pilot in the first place by holding my heading precisely on a point during the VMC demo. When my foot hit the iron stop I'd lower the nose and cut the throttle to 1/2, or more if needed. All the while, then, the plane would be slipping toward the dead engine, away from the ball indicator, not that I'd notice because I'd be looking outside. If the plane stalled first, I'd predict it would theoretically go "over the top", like all the singles I've stalled. But, since the engine is accelerating airflow over the wing there, I doubt it would stall before losing rudder authority which would trigger my recovery. So, I will postulate that a yaw string (or strings) mounted at the right place(s) might be a safety feature during a VMC demo. You'd want to keep the string showing a slip and not a skid until your foot hits the stop. In a skid, you'd go "under the bottom", with the good engine pulling you into the spin as opposed to away from a spin.

I have never been in a spin in a light twin nor on my back in one. I have flown with some highly experienced pilots who have, though, and listened to their war stories with interest. A couple have been upside down in Learjets, one during calibration of the stall warning vane in a Lear 23. Another in a Lear 35 when the cfi turned off the stall warning system to demonstrate the so-called aerodynamic warning rumble that never materialized. Another in a light twin, although I don't recall what upset the apple cart. On the other hand, there are many DPEs and CFIs who do this every day for a living. Are they all blocking the rudder? Pushing against an iron stop is pretty distinguishable. Pushing against somebody else's leg muscles, not as much. During the ensuing tug of war, I can see where the confused student could allow his heading to wander, a skid to develop and a CFI focused on the rudder blocking not notice until the plane snaps upside down. I wouldn't do it. And I'm not saying that's what might have happened in this accident. I don't know.