2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

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2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby Wm.Ince » Sat Dec 22, 2018 6:49 pm

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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby Scooper » Sat Dec 22, 2018 8:39 pm

That's very sad. Apparently the pilot was a student doing touch-and-goes and had a very hard landing.
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby drseti » Sun Dec 23, 2018 8:41 am

Sadly, I both knew the pilot and had flown that airplane. And, even before the NTSB investigates, I'm going to go out on a limb and say just what happened, because this was probably the most common accident sequence in an LSA.

Gary went off the left side of the runway during a touch-and-go. I predict they'll find that was preceded by a secondary stall just when adding full power after a bounce. It's common for the sudden air blast over the tail in this scenario to push the tail down, slowing the aircraft. In addition, the huge internal rotating mass of the geared Rotax engine causes significant gyroscopic precession when at full power. This, coupled with the already strong p-factor, can result in a hard pull to the left.

In our own Safety Corner, I've discussed gyroscopic precession. I've even done an EAA safety seminar on it. I believe the only way to cope with a bounce on landing in a Rotax-powered tractor configuration is to simultaneously drop the nose, add full power, and apply lots of right rudder. (The NTSB investigation may well find other contributory factors, but the fact that, in this scenario, the aircraft always departs the runway to the left, speaks volumes.) I'm so distressed that it takes a tragedy to underscore this.
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby chicagorandy » Sun Dec 23, 2018 8:53 am

Condolences and prayers to the family and friends involved.
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby Jim Hardin » Sun Dec 23, 2018 9:55 am

Paul: I think your predictions are in order.

I have noticed a lot of the left turning tendency even during engine idle flare and most pilots do not correct for it.

Until you have done them, it is hard to fight the PIO's and we tend to chase them trying to 'save the landing'. I always urge students to go around if they aren't stable after a bounce. Usually tell them we will log that one as a ricochet.

Really feel for the family and friends.

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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby HAPPYDAN » Sun Dec 23, 2018 10:56 am

So, is this extreme gyroscopic precession a Rotax quirk? In my many efforts at solving the landing equation, I took many serious bounces. Some I saved with a burst of power and nose-up attitude. Some were more like a springboard, requiring full power and a go-around. All this was in a Skycatcher, powered by the Continental O-200D. I do not remember any extreme left-turning tendencies beyond a normal take-off and climb-out, which in that plane is easily managed with rudder and a touch of aileron.

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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby drseti » Sun Dec 23, 2018 11:35 am

HAPPYDAN wrote:So, is this extreme gyroscopic precession a Rotax quirk?


Yes, Rotax or any other geared engine where the crankshaft and flywheel are much more massive than, and turning much faster than, the propeller.
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby drseti » Sun Dec 23, 2018 11:38 am

I've just posted the following to my flight school's email list, for the benefit of my students:

Fellow pilots,

None of us likes to dwell on the risks associated with Light Sport and General Aviation, but when that rare fatal accident occurs, we must address them. Sadly, such an accident occurred yesterday at Linder Field in Lakeland FL. As it happens, I both knew the pilot, and had examined and flown the airplane involved. What follows is my (pre-NTSB report) analysis of the accident. There are safety lessons for you to take away from this sad discussion.

Gary Mansell was a 64 year old retiree, who had bought a 2014 Bristell LSA a year and a half ago to complete his license. He was still a student pilot, and was practicing touch-and-goes solo at KLAL yesterday morning. On his third touch-and-go, the aircraft bounced, veered to the left, appears to have stalled, impacted the grass to the left of the runway, and was consumed in flames.

I think every one of my students has experienced the three main factors which contributed to the tragedy. The first problem regards recovery from a landing bounce in a light aircraft. Because of low inertia, as an LSA gains altitude after a bounce, its airspeed drops off rapidly, bringing it close to a stall if uncorrected.

The second factor is the fact that, as you add full power in an LSA for a go-around, there is a strong tendency for the nose to rise, and the plane to slow down even more. This effect is counter-intuitive; our car-driving habits tell us that when we add power, the vehicle goes faster. Not so in an airplane! Think about that sudden blast of air across the horizontal tail, which sharply increases its down-lift, potentially resulting in a secondary stall (as apparently happened to Gary).

The third factor is gyroscopic precession, a result of the high internal RPM of the geared Rotax engine, which means there is a very strong left-turning tendency during a takeoff (or a touch-and-go, or go-around, both of which involve converting a landing to a take-off). This is exacerbated by the already present left-turning tendency caused by p-factor. I've covered gyroscopic precession in an EAA webinar which you might care to review:

http://www.eaavideo.org/detail/video/4609183037001

I'm sure the NTSB report will ultimately show other contributing factors, but I think you can all understand the combination of the three factors I've listed, since you've experienced them all (hopefully, not in combination). This is one of the reasons I teach only full-stop, taxi-back pattern work -- but if a go-around is required, and started after the wheels have touched the runway, it becomes a touch-and-go, even if that's not what you intended. So, we all should review the proper recovery technique periodically.

So, what should you do if you get into this situation? You must IMMEDIATELY and SIMULTANEOUSLY:

(1) Drop the nose. That is, relax your back-pressure on the stick. You have to keep the plane from slowing down to stall speed.

(2) Feed in full power.

(3) Use aggressive right rudder to hold the plane straight.

Notice that this all happens fast. They say time is nature's way of making sure that everything doesn't happen all at once. But in this case, you don't have any time -- all this MUST happen all at once!

Notice further that I didn't say anything about retracting flaps on initiating a go-around (as is commonly taught). This is because you are too close to the ground to allow ANY distractions. And yes, an LSA will climb just fine with full flaps, in most situations (very high density altitude being a possible exception).

What about the drag from the flaps, you may ask? Remember that parasitic drag goes up exponentially with velocity. But a go-around is performed at so slow a velocity that you can consider the drag to be negligible. Once you're safely several hundred feet above the ground, there's plenty of time to bleed off the flaps and accelerate.

Thankfully, fatal LSA accidents are rare. But they can, and do, occur. Our best defense might well be to study every one, and apply whatever lessons we may learn to our own flying.

Safe Skies,

Paul
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby RTK » Sun Dec 23, 2018 3:43 pm

Excellent note and advisory for both your students and anyone else who will read it, Paul.

Condolences to you and your friend’s family on the loss.

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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby cam737 » Sun Dec 23, 2018 4:50 pm

Prayers to the pilot, friends, and family. Thanks so much for the info and thoughts Paul. Tough one.
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby HAPPYDAN » Sun Dec 23, 2018 5:55 pm

Thanks for the link to the webinar, Paul. I found it very informative.

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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby Cub flyer » Mon Dec 24, 2018 9:20 pm

Doesn’t the Rotax flywheel and crankshaft turn Opposite direction of the propeller. It would not cause a left turning tendency.

P factor would be left turning at high angle of attack. Possibly than an O-200 because of the high pitch of a geared Rotax LSA lower RPM propeller

The composite LSA propeller is much lighter than a aluminum Sensenich or McCauley.

I think look more into if the Bristell has any dampening on the nose gear strut. Just a spring instead of an oleo or some other kind of shock makes it into a pogo stick. Vertical fin size compared to RV-12
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby drseti » Mon Dec 24, 2018 11:12 pm

Cub flyer wrote:Doesn’t the Rotax flywheel and crankshaft turn Opposite direction of the propeller.

Yes, that's true.
P factor would be left turning at high angle of attack.

Correct.
The composite LSA propeller is much lighter than a aluminum Sensenich or McCauley.


Also correct. So, gyroscopic precession from the prop (such as it is) and that from the crankshaft/flywheel would act in opposite directions. When the axis of rotation is deflected upward, precession from the engine components would be to the left (same direction as p-factor). Precession from the prop would be opposite, i.e. to the right. But the prop is so light, and turning so much more slowly, that its contribution to net precession is negligible, and the net precession in both the flare and in rotation is dominated by the engine - hence, to the left.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby Cub flyer » Tue Dec 25, 2018 8:19 am

Interesting. I’m not so sure though. I don’t see a large right turning tendency with a radial engine tailwheel airplane in the landing flare or adding power to go around while pitching up. There is a tremendous amount of rotating mass with the radial and also heavy propeller turning the same direction. The crankshaft is turning opposite direction of the Rotax so if precession was dominant I should get a large right turn tendency in the landing flare. The airplane is heavier but engine weight to airframe weight is the same ratio or even more.

Here’s a copy from an interview with Andrew King and Fred Murrin at Rhinebeck NY flying WWI airplanes with Rotary engines. If there was a big gyroscopic effect they would be the ones to really notice.

According to Murrin and King, often-repeated tales about tricky aircraft handling due to the gyroscopic effects of rotating engines—that the spinning mass of the engine made for very quick turns to the right and slow turns to the left—are exaggerated. “When you hear the stories about rotary engines being hard to fly, the problem was with the inexperienced people flying them,” explained King. “When I made my first flight in a rotary-powered aircraft, I landed and then realized that I hadn’t noticed any gyroscopic effects. An experienced pilot automatically compensates for those things. Turns to the right might be a little quicker, but that is because the rotary engine tends to pull the nose down [in that direction], and you make a quicker descending turn than you make a climbing turn.”

Murrin agreed: “There are small gyroscopic effects but nothing close to the exaggerated tales often repeated in print and in documentaries. You adjust for them much the same way you would if you were flying in mildly gusty conditions. The torque reactions are most notable during takeoff and gliding in for landing when ‘blipping’ the engine.”


Anyway It’s a sad situation after this accident and I hope something can be learned to prevent it from happening again.
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Re: 2014 Bristell crash, Lakeland Linder Rgnl (KLAL)

Postby 3Dreaming » Tue Dec 25, 2018 12:52 pm

Something else to consider is the fact that Rotax engines change RPM almost instantly. Traditional aircraft engines are a slower to change RPM. So when you push the throttle forward you need to react much more quickly.


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