Scottsdale Comanche crash.

[Guest]

I assume that the CFI is the PIC and therefore he holds the ultimate responsibility for this.  The student is also his victim.

Clarence

[aviatoreb]

3 hours ago, M20Doc said:

I assume that the CFI is the PIC and therefore he holds the ultimate responsibility for this.  The student is also his victim.

Clarence

There is some official standard of fault and sometimes it seems as if it could be a bit different from the social standard of fault.  I believe the FAA will likely find both pilots at fault.

[kmyfm20s]

On 5/6/2018 at 2:54 AM, M20Doc said:

I assume that the CFI is the PIC and therefore he holds the ultimate responsibility for this.  The student is also his victim.

Clarence

I would curious about this as well. On take off the tower asked if everything was okay and one of them replied it was a training flight which I assume it was the CFI. I don't know who is responsible at that point but it sure sounded like the CFI was taking the authority for the flight.

[DanM20C]

On 5/4/2018 at 12:17 PM, gsxrpilot said:

I find with me in the front seat, it's just about impossible to create an aft CG situation in a Mooney. 

Converting a 252 to an Encore involves 10 hp and better brakes... that equals an additional 300 lbs. gross weight. I've heard it said that 252's fly all the time at Encore W&B without any issues. 

That Mooney loaded with 5 adults, one in the baggage space couldn't have been out of CG aft. Did you see the size of the boys in the front seat?

Did you see the size of the boy and girls in the back?  They were all well fed too.

The CG range on the C is from 42-49", mine had an empty CG of around 45.5".  The front seats are at 36-44".  The size of the boys up from suggest they were further back than the 36"  So I would guess 38-40 so the rear passengers could squeeze in.  The rear seats are at 70" and the luggage compartment is at 93".  So all that ballast in the front seats doesn't come close to off setting the weight in the back.  Even being charitable on the weight of the ladies in the back I can't make the CG come into limits on my excel sheet.  Granted I don't know the empty CG of that particular airplane, it had a two blade prop so would guess it would have been similar to mine.  The NTSB also pointed out they used driver licenses for the occupant weights.  Those are notoriously low, I know mine is.  The eye witness reported airplane prematurely rotating and becoming airborne several times on the takeoff run.  Sort of makes sense with an inexperienced pilot (63tt) and a heavy aft CG.     

With my K it would be impossible to load aft CG if I adhere to the gross weight and baggage and hat shelf limits.  In fact with full fuel, my self and another 200+ lbs in the right seat, it will be out of the forward limit if there is not ballast in the rear.  I think this means I need a 3 blade MT! Thanks for that 12amu idea @KSMooniac!

Note: thread drift, this is a different accident than the Comanche.

Cheers,

Dan

 

[ragedracer1977]

Final report is out.  Ultimately sounds like it was engine failure.

https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20180410X32846&AKey=1&RType=HTML&IType=FA

They guesstimate 135 over gross, but the last W&B they could find was from 1973.  It had dual 430s, so we can assume that was incorrect

They also estimate 15 lbs baggage for each person, but the videos and pictures I saw floating around don't justify that.

Even if they were 135lbs over, that wouldn't have caused this, but the engine failure sure would

[Hank]

Don't you think the lingering effects of the cocaine and ecstasy found in the "student pilot" with no cert sitting in the left seat were a factor? And maybe more likely than an engine failure, considering the ATP in the right seat answered ATC's query that they were not experiencing problems but were "in training mode"?

To me, that is much more likely than unsubstantiated speculation about engine failure.

Edited April 9, 2020 by Hank

[ragedracer1977]

Just now, Hank said:

Don't you think the lingering effects of the cocaine and ecstasy found in the "student pilot" with no cert sitting in the left seat were a factor? And maybe more likely than an engine failure, considering the ATP in the right seat answered ATC's query that they were not experiencing problems but were "in training mode"?

To me, that is much more likely than unsubstantiated speculation about engine failure.

Student pilot being part of it? Sure. The drugs? I don't know.  I'm not a doctor. But they sure spent a lot of words saying the levels were very very small.

Most likely precursor is the engine failure.  That's no longer speculation. 

[Hank]

Just now, ragedracer1977 said:

Most likely precursor is the engine failure.  That's no longer speculation. 

How do you figure? All I saw was a broken valve spring on one cylinder.

[ragedracer1977]

Just now, Hank said:

How do you figure? All I saw was a broken valve spring on one cylinder.

You don't think that's a failure? I've had a broken valve spring in a V8.  The thing would barely run.  I can't imagine a 6 cylinder engine running much better

[Hank]

Overweight, out of CG, outdated CG paperwork, unlicensed student pilot at the controls with illegal drug residuals in his system, but all unrelated to the fiery crash, which you posit was caused by a single broken valve spring. OK . . .  

[DanM20C]

5 hours ago, ragedracer1977 said:

Final report is out.  Ultimately sounds like it was engine failure.

I would classify it as Loss of Control.  The report makes no mention of any internal cylinder damage so I can assume what was left of the valve spring and keeper retained the valve.  And somehow there was still compression on that cylinder so it suggests that the valve/spring was still operating to some degree.  The engine may have been running rough and making less power but ultimately they lost control. 

This is one of those accidents where the pilot(s) stacked the deck so far out of their favor that the slightest little problem would end in disaster. 

Its was a terribly sad accident.

Dan

 

[ragedracer1977]

1 hour ago, Hank said:

Overweight, out of CG, outdated CG paperwork, unlicensed student pilot at the controls with illegal drug residuals in his system, but all unrelated to the fiery crash, which you posit was caused by a single broken valve spring. OK . . .  

Do you know what I mean when I say precursor? 

For all we know, there could have been a current weight and balance in the plane that shows they were within limits.  In fact, that's where you're supposed to keep it.  I make copies and file one away, but there's no requirement to do so 

Whatever the W&B was, it's pretty unlikely that one from 1973 was accurate given the state of the avionics that existed at the time of the crash 

An engine failure, at night into rising terrain, with a student pilot at the controls is a recipe for disaster even ignoring everything else 

[ragedracer1977]

Just now, DanM20C said:

I would classify it as Loss of Control.  The report makes no mention of any internal cylinder damage so I can assume what was left of the valve spring and keeper retained the valve.  And somehow there was still compression on that cylinder so it suggests that the valve/spring was still operating to some degree.  The engine may have been running rough and making less power but ultimately they lost control. 

This is one of those accidents where the pilot(s) stacked the deck so far out of their favor that the slightest little problem would end in disaster. 

Its was a terribly sad accident.

Dan

 

I don't know enough about aircraft engines to say.  But from my personal experience, broken intake valve spring in a Dodge V8, it could be a bad day.  The engine lost a ton of power, would'nt accelerate, and ran awful.  I thought a rod blew out of the block. In the end, there was zero damage to the engine.  I replaced the $2 spring and it ran like a top.

Like I just posted above, I agree.  The pilots did a terrible job stacking the deck 

[David Lloyd]

A non-functioning exhaust valve generally affects only one cylinder.  A non-functioning intake valve, if open affects all cylinders.

[Ron McBride]

I had an engine failure in a C310. I broke an rocker tower on 1cylinder on a6 cylinder IO470.  That engine would only produce about 1500 rpm with the throttle reduced on the ground.  Failure was on the runway just before rotation, fortunately a wide runway. If this happened 2 seconds later, it would have been feathered and hopefully flown around the pattern.  Scary times.

A single heavy at night, no thanks.

Ron 

[EricJ]

2 hours ago, ragedracer1977 said:

I don't know enough about aircraft engines to say.  But from my personal experience, broken intake valve spring in a Dodge V8, it could be a bad day.  The engine lost a ton of power, would'nt accelerate, and ran awful.  I thought a rod blew out of the block. In the end, there was zero damage to the engine.  I replaced the $2 spring and it ran like a top.

Like I just posted above, I agree.  The pilots did a terrible job stacking the deck 

Aircraft engines like we use have two concentric springs at each valve.   The report says the outer spring had failed, which suggests the inner spring was still functional.    I don't know how much power loss one would expect on that particular engine at takeoff rpm with only the inner spring working.   The cylinder should still be producing power, but I don't know how much less than usual.

Definitely a sad one.   I think about it every time I drive through that intersection.

[DonMuncy]

I had a broken rocker shaft boss on a 231. I can not remember whether it was an intake or exhaust. There was a definite loss of power, but far from total. 

[jaylw314]

"Examination of the three fracture faces using a scanning electron microscope revealed that two of the fractures initiated at pits on the inside diameter of the helix and propagated due to fatigue crack growth through about 40% to 50% of the diameter before final fracture due to overstress. "

To me it seems possible the spring was intact until the accident, and then fractured at the time of impact, so not a slam-dunk that its failure contributed to the accident, especially if there were two fatigue fractures.  It's hard for me to imagine that two separate fatigue cracks would fracture at the exact same moment spontaneously due to normal operation, since those fatigue cracks had presumably been there for some time.  Intuitively, I can believe the crash impact fracturing an already weakened spring in two places simultaneously.

[kmyfm20s]

I had an outer valve spring break and I couldn’t tell any difference in power. I only found it because in was getting aluminum specks in my oil filter and started looking for the source. I guess in this case having 3 pieces of the outer spring floating around it could have bound up with the inner spring preventing the valve from functioning properly. 

The only time I have had noticeably less power with the engine not sounding right was with a couple of magnetos failures.  Unfortunately in this accident they were damaged in this crash. 

With the instructor in the plane I don’t feel like the trace amount of drugs in the student played any part in the crash, just my opinion. 

[N201MKTurbo]

I had a broken outer spring on an intake. I didn't know it was broken until I took the rocker cover off. 

[jaylw314]

15 hours ago, kmyfm20s said:

I had an outer valve spring break and I couldn’t tell any difference in power. I only found it because in was getting aluminum specks in my oil filter and started looking for the source. I guess in this case having 3 pieces of the outer spring floating around it could have bound up with the inner spring preventing the valve from functioning properly. 

The only time I have had noticeably less power with the engine not sounding right was with a couple of magnetos failures.  Unfortunately in this accident they were damaged in this crash. 

With the instructor in the plane I don’t feel like the trace amount of drugs in the student played any part in the crash, just my opinion. 

It's worth noting that while we think of the intoxication state of cocaine as lasting only several hours, there can continue to be significant psychological and cognitive impairments in the recovery stage (the next 1-2 days) after heavy use.  Since cocaine is generally only detectable within 48-72 hours of last use, I'd think it remains at least a possibility there were still some impairments (especially given the knowledge of multiple substance use simultaneously), although to be more certain would require knowledge about his prior pattern of use.

A good analogy would be someone who gets s--t faced drunk one night, and goes flying the next morning.  The amount of alcohol in their system is zero, but I think most of us would agree flying with a massive hangover is not a particularly good idea.  The level of impairment is not simply proportional to the amount of intoxicant in question.

[N201MKTurbo]

Why does the condition of the student even matter? The CFI is supposed to keep the airplane from crashing no matter what the student does. 

That being said. taking off with an overloaded plane requires extra airspeed. The climb gradient is going to be shallow and if the engine power was suddenly reduced, a rookie reaction would be to maintain altitude not airspeed, but the CFI should have taken control before the stall.

How often do we practice power failures after takeoff? Most people don't. It takes a huge push to maintain airspeed and you have to do it quickly.

[kmyfm20s]

1 hour ago, jaylw314 said:

It's worth noting that while we think of the intoxication state of cocaine as lasting only several hours, there can continue to be significant psychological and cognitive impairments in the recovery stage (the next 1-2 days) after heavy use.  Since cocaine is generally only detectable within 48-72 hours of last use, I'd think it remains at least a possibility there were still some impairments (especially given the knowledge of multiple substance use simultaneously), although to be more certain would require knowledge about his prior pattern of use.

A good analogy would be someone who gets s--t faced drunk one night, and goes flying the next morning.  The amount of alcohol in their system is zero, but I think most of us would agree flying with a massive hangover is not a particularly good idea.  The level of impairment is not simply proportional to the amount of intoxicant in question.

While I agree that impairment can be long lasting I don’t consider it to be a factor in this accident, just my opinion. That’s what the 5000+ hour ATP rated instructor was there for. The left seat party animal person didn’t matter.

[Ross Taylor]

Totally off topic...or maybe not...since getting drunk the night before was mentioned.  I know alcohol isn't a factor in this crash, but alcohol impairment was part of my first career.  Well, that didn't sound quite right did it?  Anyway, interesting fact...a "standard" 170-pound male metabolizes alcohol at a rate of about .015/hour.  So, if you're a .20 drunk it will take a bit over 13 hours before your BAC is back down to 0. Not to mention the groggy aftermath that @jaylw314 mentioned. Okay, carry on...

[ragedracer1977]

2 hours ago, Ross Taylor said:

Totally off topic...or maybe not...since getting drunk the night before was mentioned.  I know alcohol isn't a factor in this crash, but alcohol impairment was part of my first career.  Well, that didn't sound quite right did it?  Anyway, interesting fact...a "standard" 170-pound male metabolizes alcohol at a rate of about .015/hour.  So, if you're a .20 drunk it will take a bit over 13 hours before your BAC is back down to 0. Not to mention the groggy aftermath that @jaylw314 mentioned. Okay, carry on...

Yet for whatever crazy reason, you can go on a bender and be legal to fly 8 hours after your last drink, but you can’t have a single glass of wine at a 5pm dinner and fly home at 9pm