Crashing a Belite Airplane

Crashing a Belite Airplane

(c) 2014 by James Wiebe

Chapter 1:  THE EVENT

An Observer saw it happen, and commented as follows:  “The plane had entered a departure stall, then spun into the ground.  When the Belite hit the ground, it sounded like a grenade went off.”

The Observer had past military experience, and brought his remembrance of ugly scenes into his thoughts:  “I ran up to the point of impact, expecting to see a bloody body.  Instead, the pilot was walking around the crashed Belite, looking at the wrecked airplane.”

The Belite UltraCub had just had its first major accident.  I’d received the call from the Observer (who happened to be the owner of this particular Belite, and our customer), and the very next day I was having lunch with him, along with the pilot who’d survived the stall / spin / smash accident.

I’d never heard of someone surviving a stall / spin, much less surviving without hardly any damage to their own body.

We’ll get to the pilot’s story in a few paragraphs.  In the meantime, the pictures of the wreckage tells a fascinating tale of impact energy, dissipated by a cabin constructed of aluminum, with impact loads absorbed by the Belite Ultracub’s lightweight and strong boxed aluminum structure.

Here’s a view of the accident site, exactly as it was:

A wrecked Belite, after a stall / spin into terra firma.  The pilot survived with a scratch and two bruises.

A wrecked Belite, after a stall / spin into terra firma. The pilot survived with a scratch and two bruises.

Chapter 2:  THE AIRCRAFT’S STORY

According to the Observer, the aircraft hit the ground at an impact angle of around 45 degrees.  The impact caused the following damage:

  • The carbon fiber composite propeller was destroyed.  Well, of course…
  • The single cylinder Hirth F33 engine was severely damaged.  As the engine was mounted cylinder down, the muffler and cylinder head sustained damage.  The redrive was not damaged.
  • The motor mount was destroyed, bent downwards by the impact to the engine lower side.
  • The front cabin angle aluminums were severely bent.  These angle parts are supported by gussets.  OK, a lot of stuff was severely bent!
  • The wings appeared largely undamaged.  (One wing which had hit a wingtip had subtle but substantial internal damage – the sail / anti-sail tubes were either bent in compression or snapped in tension; the main spar and false rib spar had a subtle bend.  The other wing had one sail / anti-sail mount fitting sheared off from the spar.  You can see the subtle bend in the front wing spar in the above photo.)
  • The impact of the wings caused their AN-5 attachment bolts to bend – a shear stress load which was many, many thousands of pounds.  The top cabin cross connection tubes had deformation damage around the attachment bolts.  These cross connection tubes are constructed from 6061T6 1” square aluminum, with a wall thickness of .063.  Their partial deformation indicates that the shear load at the bolts (and the consequent deformation of the aluminum) was approximately 9000 pounds.
  • The landing gear had bent backwards and upwards, folding into the underside of the cabin and tucking upwards towards the pilot’s bottom.  (But the landing gear and wheels never reached the pilot’s lower torso).
  • The rear fuselage had a couple of bends in the aluminum longerons, immediately below the tail feathers.  These compressive bends were caused by forward impact G forces of the tail feathers, transferring into the rear fuselage.  The G force required to bend the 2024 aluminum alloy extrusions is difficult for to calculate, (because of Euler’s buckling principles), but I’ll take a stab at it – a force of around 1000 pounds was required to bend these longerons.  So perhaps the momentary G forces on this area of the structure were around 50 G’s, based on a tail feather weight of 20 pounds.  Truly this is guess-timation.

Here’s a look through the top of the cabin, taken directly downward at the pilot’s seat:

The wrecked cabin of a Belite UltraCub aircraft.

The wrecked cabin of a Belite UltraCub aircraft.

The Belite UltraCub’s cabin is composed of two aluminum side boxes and four cross boxes.  The side boxes run along the sides of the cabin, and they absorbed crash loads from the front of the cabin heading backwards; the four cross boxes under the pilot absorb loads coming up from the ground and protect the bottom part of the pilot’s torso.  Three of these undercabin cross boxes are partially visible in the above photo.  The front cross box is clearly visible, just above the control stick, with two lightening round holes of about 3” diameter.  These boxes are constructed from square tubes with very thin walls and from a front side and a backside continuous aluminum frame/gusset, which spans the entire length of the tube.

Note that the pilot’s seat is bent but intact.  Not visible below the pilot’s seat is what I call a “butt plate”, which is an aluminum plate with angle reinforcements below and extra gussets.  It did its job very, very well.  It connects to two of the cross boxes, and the pilot seat sits on top of the butt plate.

The four point safety harness did its job.  It did not break.  In the event that it had failed, the pilot’s head and torso are likely to have impacted forward, with severe consequences.

Our cheap $12 fuel tank from the home improvement store held together without any problems.

Fuel tank in a wrecked Belite ultralight airplane

Fuel tank in a wrecked Belite ultralight airplane

Chapter 3:  THE PILOT’S STORY

Now, back to the pilot’s side of the story: he had a small round scrape (about the size of a large coin) and a couple of bruises.  He was fine, but in some sort of reasonable shock as to what had just happened.  The Belite UltraCub cabin had crushed, like an accordion, collapsing around the pilot.  No broken body parts, no lacerations.

The pilot’s story:

“I’m a multi-thousand hour commercial pilot.  I have a lot of flying time in general aviation aircraft, and I fly for a living.  I’m embarrassed by what happened, so I’ve chosen to remain Anonymous.  I’ve also chosen to share this story with others, so that the pilot community can learn from what happened.

“I’d never flown an ultralight aircraft before, much less one with just 28HP, but I was eager to try it.  Although I’d been warned not to over pitch the initial climb, that is, in fact, what I did.  I climbed through ground effect, then it felt like I lost control of the aircraft, but what was really happening was a departure stall, which quickly turned into a spin.  When I realized what was happening, I slammed the stick forward and recovered just as the aircraft impacted the ground.  Of course it was too late.  A few seconds later, I was out of the aircraft, walking around the wreck, and pondering what had just happened.

“In hind sight, it’s so obvious:  allow the aircraft to gain speed before climbing out of ground effect.  Listen to what I was briefed on.  Perhaps spend more time acquainting myself with the aircraft in ground effect hops.

“The next time I fly this aircraft–and I will fly it again after it is repaired and rebuilt–I will note the indicated airspeed at lift off and keep a healthy margin of additional speed until I flare to land!

“I am amazed that I came through this essentially unharmed.   What a great job Belite has done making this aircraft safe.  One might say the Belite people protected me from my own mistakes.

Chapter 4:  EPILOGUE

The aircraft is currently being rebuilt.  As stated, the rear fuselage had a minor bend in the lower longerons, which we easily repaired.  One wing is being replaced, the other wing is being repaired and the cabin is being replaced.  One tail feather had a minor bend in the Chromalloy steel, also easily repaired.  The engine has been repaired, and is awaiting installation.  A new Ivoprop composite propeller will be on the rebuilt aircraft.  As of this writing, the first flight of the rebuilt aircraft is scheduled for late April.

I can’t express strongly enough how pleased I am with the crash capability of the cabin.  Everything in the cabin structure ‘gave up’ under mostly compressive forces in a way which unwound energy from the impact, without causing any appreciable damage to the occupant.

If I wanted to add more strength to the cabin, I would add it on the side boxes, but this would be at the expense of weight, and FAR Part 103 is always a balancing act between the mandate for low aircraft weight and safety.  According to the law, it’s more important that the aircraft be light than it be strong.  Such is the oddity of Part 103.  Part 103 is not a safety standard, it is a weight standard.  Sigh.

Another concern is lacerations caused by sheet metal.  A possible solution is the use of rubber slip-on edging, especially around the interior pieces of the cockpit.

I’m aware of a lot of aircraft accidents.  I’ve lost a Belite customer to an aircraft accident – but not in a Belite.  He had a departure stall in a Rotax powered aircraft of another experimental design.  We’ll never know the exact details, but things went very poorly for him.  So I know how these kinds of takeoff accidents often end – poorly.  I’ve also heard of a new owner who crashed his Kitfox Lite on his first departure.  He did not survive.  That was with an engine significantly larger than our F33 28HP Hirth, but also at a higher field elevation.  The original KFL looks a lot the same, but uses a different wing, (smaller), different flaperons (smaller), different fuselage (steel instead of our aluminum), and other differences as well.

I have developed very strong personal biases towards my aircraft design.  We’ve lost sales of Belite Aircraft over perceived differences in design philosophies vs. competition, and this maddens me.  I’m aware of what happens when a non-enclosed light or ultralight aircraft impacts the ground, with the pilot’s feet literally hitting the ground before the aircraft structure.  It rarely ends well for the pilot.

I’m also confident that some percentage of the readers of this article will think I’m wired a little oddly for publishing this article.  Yes, I am.  Ultralight aircraft accidents are never investigated by the FAA, and pilots rarely ‘fess up to how that stall-spin accident actually occurred.  This is a unique opportunity to see what happened to the airplane, and hear what we can learn from the pilot’s story.  Let’s do that.

It takes a little bit of bravery to publish this story.

I haven’t hid the fact that this event happened:  We’ve had prospective customers come to our facility and see the wreck, and then order our assembled aircraft or kit.

If you have any questions about this, please send them to info AT beliteaircraft.com

Here are several more photos of the wreck:

Wrecked engine, mount and prop on a Belite UltraCub

Wrecked engine, mount and prop on a Belite UltraCub

Cabin view inside a wrecked Belite ultralight airplane

Cabin view inside a wrecked Belite ultralight airplane

Gear folded up under Belite UltraCub ultralight wreck

Gear folded up under Belite UltraCub ultralight wreck

Bent rear fuselage aluminum angle longerons

Bent rear fuselage aluminum angle longerons

Cross tube on top of cabin showing deformation

Cross tube on top of cabin showing deformation

Wing attachment bolt, AN5, showing bend.  9000 pounds of shear?

Wing attachment bolt, AN5, showing bend. 9000 pounds of shear?

Ridiculous Base – Final Turn Photo

Our friend Paul Fiebich took some awesome photos of the UltraCub at Airventure.  One of them does an excellent job of capturing the sharp turn required to navigate the base to final turn at AirVenture.  He also captured many other unique perspectives on the Belite.

Please enjoy these photos; my thanks to Paul for letting me use them on the blog.

Ridiculous turn to final at #Osh13

Ridiculous turn to final at #Osh13

Image

Belite UltraCub moves down the runway

Image

View from the ‘tower’ of a Belite UltraCub

F2

Christian gets ready to hand prop the engine. In the conga line at AirVenture.

F3

Takeoff and nice climbout established. Photo from the viewing stand.

F6

Another view of an excellent climbout.

F8

UltraCub taxiis to takeoff.

F9

UltraCub passes overhead.

F10

Am I landing or taking off?

F11

Beautiful photo of metallic burgundy / brass ultracub against blue sky and clouds.

The only version of Windows or Doors which works on Belites

Apologies to Microsoft.  Everyone knows that Windows 8 is horrible on laptop computers.

But I digress.  I really want to talk about windows; actually I want to talk about doors on Belite ultralight aircraft, especially our UltraCub.  We get asked a lot about this feature, and it is worth explaining.  Our door kit is very sharp:  built from CNC cut aluminum parts and CNC cut polycarbonate, the door ends up as an exact fit on your airplane.

Take a look:

Door on Belite

Door on a Belite ultralight airplane.

hinge along top of door

Hinge line along top of door.

opening the door

Opening the door. Note the neat rivets (because the holes were predrilled.)

Pins on door

Locking pins on the inside of the door.

Polycarbonate on pilot side

Polycarbonate on pilot side of the airplane. It comes precut from Belite.

small window

It’s not part of the door kit, but we did install small windows in the corners as shown.

Photos: Takeoff Sequence in a blue Ultracub with tricycle gear

Really cool photo sequence of blue tricycle gear ultracub taking off.

Takeoff of blue ultralight airplane from Belite.

Takeoff of blue ultralight airplane from Belite. Beginning the ground roll.

takeoff of blue ultralight tricycle gear airplane from Belite.

Takeoff of blue ultralight tricycle gear airplane from Belite.

Takeoff of blue ultralight airplane from Belite.

Takeoff of blue ultralight airplane from Belite. Looks like only one wheel is still touching?

Takeoff of blue ultralight airplane from Belite.

Takeoff of blue ultralight airplane from Belite. Everything off the ground.

Takeoff of blue ultralight airplane from Belite.

Takeoff of blue ultralight airplane from Belite. Gaining a little speed in ground effect.

Takeoff of blue ultralight airplane from Belite.

Takeoff of blue ultralight airplane from Belite. Nice climbout started.

Climbout of blue ultralight airplane from Belite.

Climbout of blue ultralight airplane from Belite. Rapid ascent.

 

 

 

 

 

 

Upgrades to Ultralight Aircraft, Actually

I arrived in Oshkosh earlier this evening.  After a nice ribeye steak, it’s back to the house and (finally) time to start updating you on the many, many things that have happened at Belite over the last few weeks.

Starting with our demonstrator aircraft, which we call Burgundy II.  This airplane is a four color artistic beauty:  metallic burgundy with brass color, along with white and black trim.

It was awesome at Sun N Fun.  It is more awesome at Airventure, as we’ve improved it, again.

  • Still with a reliable four stroke 45HP engine.
  • Carbon Fiber winglets.
  • New metal cowling.
  • Best ever instrument panel, custom cut in metal.
  • Dual ignition:  magneto / electronic.
  • Improved firewall.
  • Improved horizontal stabilizer.
  • Attention to detail throughout.
  • New fuel tank — clear plastic.  Easy fuel level visibility + fuel probe.

New look on the flaperons with improved trailing edge treatment.

The pictures are proof.  Let’s start by looking at the instrument panel.  We have, from Left to right:  Dual ignition switches, Tiny Tach (inset into panel), oil pressure from engine, fuel gauge, G meter, dual EGT, Turn Coordinator, Angle of Attack indicator, Airspeed, VSI/AGL, Digital Altimeter, and voltmeter.  With the exception of the oil pressure and the voltmeter, all of these instruments are from Belite.  Including the newly announced Angle of Attack (AOA).  Isn’t this what you want in your panel?

New instrument panel.

New instrument panel.

Now let’s look at the wing improvements.  The following photo shows the carbon fiber winglets, (new option — $500 for a pair) along with a one-off detailing on the flaperon utilizing a very thing aluminum trailing edge reinforcement.  It looks extra sharp.  This is how you want your airplane to look.

Winglet and flaperon on Belite aircraft.

Winglet and flaperon on Belite aircraft.

Let’s take a quick look at the dual ignition switches:  one is to the magneto; the other is to an electronic ignition system.  My Belite is now more advanced than the vast majority of general aviation aircraft.  🙂  Your ultralight airplane can have dual ignition as well.

Dual Ignition (electronic + magneto)

Dual Ignition (electronic + magneto)

The new metal cowling is easy to build, and is constructed from CNC cut pieces of flat aluminum, which are riveted together, forming a very nice three dimensional shape.  This cowling is held in place by three nut-serts on each side and is rock-rigid in its attachment to the airplane.  It is far better than our fiberglass cowl (now discontinued).  The new aluminum cowl holds the windshield in place, decreases airframe drag, and allows builders to custom add flat aluminum to the sides to match their engine.  Builders are also encouraged to add a foam plug to the front, in order to finish the cowl look, should they desire.  (We haven’t done that yet, but will.)

Burgundy Ultracub with cowling attached.

Burgundy Ultracub with cowling attached.

(The cowling hadn’t been completely painted when the above picture was taken.)

The winglets are CNC cut from carbon fiber, and are offered as a new add-on kit ($500) which screws onto the wingtips.  Removable for flight, we don’t count their weight in the final weight of the aircraft, but it’s not a lot.  I attached them with stainless steel screws (but I should have used titanium screws to avoid long term corrosion issues.)

Winglet on Belite ultralight airplane.

Winglet on Belite ultralight airplane.

The tip ribs on the horizontal stab / elevator were inwardly warped, due to fabric tension.  We glued on some foam blocks, sanded them perfectly, and over-covered with brass oracal trim.  It ended up looking fantastic.  If you had an ultralight airplane, you’d want the tail to look like this:

Beautiful detail on horizontal stabilizer and elevator.

Beautiful detail on horizontal stabilizer and elevator.

I flew the plane several times.  I am pleased to report that our aircraft has improved again — the impact of the cowl on aerodynamics is most pleasing, and the look on the ground raises our reputation and quality to a new level.

Gene and Christian attach turtledeck.

Gene and Christian attach turtledeck.

In anticipation of your many questions, here’s some Q&A:

1.  What does it weigh?  The minimum flying weight for this aircraft is calculated as follows:

  • Base weight:  276.80 pounds, measured July 21, 2013.  Many items to be removed or added.
  • Add:  Fuel tank with probe.  1.75 pounds.
  • Remove:  1 quart of oil.   -1.87 pounds  (not actually done, engine has two quarts but will run on one.)
  • Add:  Hand toss parachute, 9.1 pounds as installed (24 pound allowance by FAR 103)
  • Remove:  Windshield, 4.0 pounds (not actually done, but could be as windshield is screw – removable and not necessary for flight)
  • Remove:  Panel, 1.2 pounds (not actually done, but could be as we frequently fly our planes without any panels whatsoever)
  • Swap:  Fuel tank platform swapped for lighter design, saved -0.88 pounds
  • Remove:  Excess steel tubing on elevator post:  -0.28 pounds
  • Add:  flaperon trim, +0.70 pounds
  • Add:  secondary electronic ignition, estimated at 1.50 pounds
  • Add:  additional firewall piece, +0.25 pounds
  • Remove:  magneto; -4.50 pounds, estimated (No, we didn’t actually do this.  You are welcome to do this when you buy the aircraft.)
  • Final minimum flying weight:  277.38 pounds (vs. FAR 103 maximum of 278 with parachute).

2.  How fast will it cruise?  A:  about 61 mph, although it may be a little faster now with the improved cowl.  (FAA maximum full power cruise is 55 KIAS / 62 mph).  If your aircraft is too fast, you are required by FAR 103 to throttle stop the engine.

3.  What is the gross weight and useful load?  A:  550 pounds / 272 pounds, respectively.

4.  Is it for sale?  A: This may be the finest new U.S. legal ultralight for sale on the planet.  It is priced at just $35K FOB Wichita (or Airventure!)

5.  What kind of engine is installed?  A: 1/2VW 45HP bored / stroked engine, constructed from a brand new cut case and nickasil cylinders.  Hand propped, starts easily.  Consumes about 1.75 GPH at low cruise.

6.  What other features does it have?  A: aluminum ribs, spring gear, independent disc brakes, angle of attack indicator, storage compartments, folding removable seat, four point harness, titanium axles, composite tail spring, foldable wings, steerable rear wheel.

7.  Could anything be done to reduce weight further?

Yes.  The wing and lift struts could be upgraded to carbon fiber, saving up to 15 pounds.

8.  Where can you go in an airplane like this?

Well, you’ve read this far, so let me show you a nice field I recently flew into.  Look at the length of the grass:

Nice runway.

Nice runway.

And look at how beautiful the strip is:

A nice place to take a Belite.

A nice place to take a Belite.

This is the kind of place a Belite can fly into.

Harvest

Weather is finally allowing some flying.  Got to see God’s view.

Today, while I was waiting for my guys to get a particular piece of work done, I had Christian prop the UltraCub so I could get flying.  I was aloft a minute later.

90+ degree heat on the ground turned to air conditioning as I climbed thru 100′.  Lovely feeling as the air pressed by on either side of me.

Still skies.  Even in the heat.  Pulled back to probably 50% power and loitered at 800′ while turning lazy circles.  Kept the air conditioning on.  Didn’t do anything stupid.  Just puttered around.

(Can’t understand why the world isn’t beating a path to Belite’s door.  Just can’t.)

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