Wednesday, October 20, 2010

Shortly after liftoff, the plane stalled, and then glanced hard into the runway...

Let's all learn from this: a Belite trike had a landing accident yesterday. 

My first thought after it occurred was that I would not take pictures; nor would I blog.  That was an expected first reaction; but incorrect.  I saw it happen; I can still see the whole sequence of events like a motion picture, in my mind.  With permission of the customer pilot, I am now blogging on what happened.

No one was hurt; and the plane was not badly damaged.  And I'm weirdly pleased with how the nosewheel took the blow and then failed in a manner which protected the pilot and the remainder of the airframe.

This particular airplane was equipped with the very strong Compact Radial Engine MZ-201.  I have flown this particular plane many times; we'd sold it and upgraded several features of the plane, including the engine.  We'd also added an inexpensive Second Chantz ballistic chute.

A transitioning pilot was practicing a takeoff roll in the bright yellow Belite.  Although this particular roll was to achieve a height of no more than about 6 inches; it didn't work out that way.  The pilot had been practicing taxiing and had demonstrated proficiency in low and high speed taxiing -- it was time to focus on the transitional takeoff attitude.   

I observed the plane rotate; the pilot quickly leveled the wings.  But by then, the plane was already quite a few feet off the ground and climbing...

In order to cancel the climb, the transitioning pilot cut power, and then the plane angled back towards the ground at a descent angle of perhaps 7 or 8 degrees.  This was probably an inadvertent departure stall.  The plane struck the runway very hard on the nosewheel, which folded under the airplane.  The plane skidded to a stop, briefly tipped sidewise and up onto the left wing, then settled back to the ground.  The main gear were still intact.  It was as if the plane was kneeling forward on its broken nosewheel.

By the time I had made it over to the plane, my customer friend had climbed out of the plane.  He was absolutely fine:  not a scratch, not a bruise.  He was even in amazingly good spirits, all things considered.

We rolled the plane back to the hangar. 

Here's an inventory of the damage:

Carbon Fiber firewall:  undamaged
Left Wing front spar (it hit the ground):  undamaged  (the spars are open and we can easily inspect on inside)
Engine:  undamaged (sheared blades and PSRU provide really good protection to engine)
Propeller blades:  destroyed
Propeller hub:  undamaged
Nosewheel landing gear:  folded under and destroyed
Nosewheel aluminum / delrin assembly and wheel:  no damage whatsoever, even after scraping along ground, but jammed against muffler
Left wing carbon fiber spar, which struck ground:  absolutely no damage
Left / Right nosewheel landing gear braces:  folded under, destroyed
Fuselage front cross member:  1/2 inch bend
Instrument panel bottom cross member (receives nose wheel landing gear strut)  1/4 inch bend

Here's a closeup of the bottom damage:

Nosewheel Destroyed on Belite Trike

 Here's the same thing, after removal of the nosewheel.  This clearly shows how the nosewheel strut has absorbed the blow, along with the nosewheel cross brace struts:

Bent nosewheel strut on Belite, with wheel removed
Look at the above picture very closely, one more time.  You can see the following:

a) bent nosewheel strut
b) bent cross braces
c) very slight bend in fuselage cross brace member (pushed back about 1/2 inch)

Just to make it crystal clear, here's a photo which shows the fuselage cross brace member:

Here's the basic process to repair the airplane:

1. Unbolt the nosewheel strut from the plane.  It has a bolt in the fuselage cross brace member (bolt hole visible in above pic) and below the instrument panel (not pictured).  Then remove.

2.  Remove fabric from front bottom of airplane.

3.  Cut out bent cross tube.

4.  Cut and weld in replacement section and nosewheel strut receiver.  Use doublers as necessary.

5.  Repair fabric.

6.  Insert new landing gear strut and cross braces.

7.  Replace propeller blades.
8.  Inspect & fly.

How did the nosewheel strut perform under this failure condition? 
Everything worked as planned. 

a) The landing gear did not 'jam' up and into the cabin.  Both the lower fuselage cross member and the top receiver cross member exhibited backwards force, but very little bending.

b)  The landing gear did fold underneath and backwards.   In fact, a careful inspection of the nosewheel strut shows that it had gross bending failure at two places, and a minor bend at a third place.  These bends each absorbed substantial energy from the impact, shielding the pilot.

c)  After the landing gear folded under the plane, the plane then skidded along the ground.  The plane did not flip over.

d)  The main landing gear were not damaged or affected.

e)  The 4130 ChromAloy fuselage provided 100% protection to the pilot.  (The 3 point safety harness was an essential piece of his protection.  His torso could not roll forward.)

f)  The damage is easy to repair.  We already had replacement parts in stock.

This happened yesterday.  With the exception of the propeller replacement, the bird should be ready to fly again tomorrow.

1 comment:

Rob Riggen said...

This is an unfortunate incident, James but the positive outcome aside from nobody being hurt is the proof of crash-worthiness. Thanks for sharing!