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INCIDENT AT OSHKOSH
(From CP38, page 10, October, 1983)
The following is a letter from Ken Swain on his
incident at Oshkosh, 1983. We have printed the letter in its entirety as may be it will
help someone in a similar situation one day.
"On August 2, 1983 my VariEze N4ZZ suffered a total power loss over Lake Winnebago and was substantially damaged in the ensuing off airport landing. Since it happened at the EAA Convention, there were a lot of stories that were semi-correct floating about. I would like to give the complete one to C.P. for dissemination along with my personal analysis of the apparent causes. Also, while I in no way consider myself the worlds most experienced pilot, I do believe that my recurrent emergency training as an active duty, current Air Force pilot gives me a perspective on emergencies not held by the average private sportsman pilot. Hopefully some of the low time EZ drivers can get some food for thought from my actions.
THE FACTS: The flight before the ill fated one was the Oshkosh 500. During the race I noticed that the fuel flow would occasionally drift up from the set 6.4 gph to 9.5 gph. Since additional leaning had no effect I concluded that my Compucruise had swallowed a few bad electrons and would have to be looked at after the Convention. Each drift up episode lasted only 15-20 seconds. I completed the race, bought 9.5 gallons of gas, and 2 hours later took off in a flight of 10 race aircraft to return to the Convention as the beginning of the preairshow. We were on downwind, over land, within landing distance of the field when we were sent to a VFR holding pattern over Lake Winnebago. Five to ten minutes later we were cleared for approach and we headed for the field. I soon reduced power to idle to slow to gear lowering speed, got the gear down, then left power back until I hit pattern speed. When I advanced the throttle there was no response. Tach showed windmilling RPM and all temperatures and pressures were in the green. My position was approximately 1 1/2 to 2 miles from shore over the lake at 1000 ft agl at 100 mph. I immediately initiated a turn towards the closest land while switching to the header tank. I then raised the gear and slowed to best glide for aircraft. While cycling mags, mixture, and throttle I made my first of two terse unanswered radio calls: "4ZZ has lost power over the lake and is attempting to reach the shoreline just south of Oshkosh". By this time I was 1 mile from shore and the prop had stopped. A cornfield was the only area that wasnt wet, hard (trees, houses, wires) or full of people that was clearly within my small energy envelope.
I kept my eyes on it while I made my last airborne call: "Hey people, listen up. 4ZZ has lost power over the lake and is headed for the shoreline just south of Oskosh". There was a strip of grass running through the field so I decided to try for it. I cleared the 75 ft. tall trees at the shoreline by about 20 feet, lowered my gear again and made a left turn to line up with the length of the cornfield. Just prior to touchdown I slowed to between 50 and 55 mph indicated, a speed I have often flown during flight tests. As I touched down it turned out the ground beneath the grass was not level and the grass to my left was taller. The left main then failed tortionally, pulling the nose left, causing the aircraft to enter the corn. The nose was now pointing 45º to the left of the motion vector. The aircraft wound up on the nose and right main gear. The momentum continued the rollover on the right canard tip and wing tip. The canopy shattered as I hit the ground inverted. The aircraft came to rest on the rollover structure and the remains of the rudder tips. The nose of the aircraft was pointing 90º to the left of the direction of landing. I was about 100-150 yards from the lake, hanging in the straps, trapped in the wreck. I dug my head set out of the dirt where the front of the cockpit used to be and got off one call to Johnny Murphy who was circling overhead, to let him know I was OK. Then I smelled gas so I shut off the master.
AIRCRAFT damage besides the rudders and canopy, the main gear strut is failed tortionally on the left and right sides. The right gear attach is 100% intact. The left tabs and attach are intact but the pad layup has separated from the strut on the front half. The motor mount failed in tension at the first welds at each bottom corner the aluminum extrusions are intact. Wings are intact. The right strake tank is separated from the spar all the way around and leaking freely. The left tank appears to have held, with minor fill cracks. Compression damage done to the inboard rib of the right aileron by the cowling are intact. Seat belts and attach are 100% intact. The forward fuselage sides and top will have to be completely rebuilt from just in front of the instrument panel forward. Nose gear, strut and box are intact. F28 is broken in two places. F22 broke in 6 places. The cop right longeron is crushed. The canard lift tabs are twisted and the outer left of the right tip will have to be replaced. The possibility of damage exists in the canard center spar but I have yet to strip the cover off the canard center to inspect it.
POST CRASH INVESTIGATION When the wreck was pulled off the trailer used to get it back from the cornfield, the engine started on the fourth blade and ran strong. After shutdown a small but steady stream of fuel ran from the carburetor. Tapping on the bowl eventually made it stop. Later, with representatives of both the FAA and NTSB present, the fuel system and carburetor were disassembled and inspected. There was some sand in the VA-6 fuel filter. There were a few infinitesimal slivers of teflon tape and a small amount of fine sand in the carburetor bowl. Less than 200 gallons of gas had been run through the system since cleaning at annual on June 30. The needle valve was clean and free and the float was undamaged. There was extensive fuel staining of my brand new ram air elbow.
MY ANALYSIS OF THE CAUSE: first, I totally rule out carb ice. I have 800 hours experience with my Lycoming and have only had it ice a couple of times in the most severe carb ice conditions. What I believe happened was this: One of the four FB0s that I bought fuel from after my annual passed some sand along with the fuel. Some of that sand eventually made it through the filter and was intermittently preventing my needle valve from closing completely. The teflon tape shreds could also have done it but there were only 3 of them and there were lots of grains of sand, 300 to 400 grains. Under pressure from the fuel pump the bowl would then overflow out the atmospheric vent, into the elbow. I believe the high fuel flows I noted during the race were grains of sand in the process of passing the needle valve. Since the power setting was high, the engine just ran a bit rich for a short while. The worst case would be to experience a needle valve clog at the moment of quickly reducing power to idle. The engine would then flood since fuel pump output is proportional to prop rpm, not power demand. It would be so loaded up that it could take quite a while to clear. Certainly more than the 15-20 seconds of windmilling prop time that I had.
Other support for this view: 1. The stream of gas from the carb after shutdown and the fuel stains on the elbow where 2 hours earlier there were none. Also, at the completion of the Oshkosh 500, Gene Sheehan looked at my exhaust stacks and commented on how lean I must have been running the race since they were almost white on the inside. After the crash and at most 10 to 15 minutes of flight, they were heavily caked with black soot.
MY ANALYSIS OF MY INFLIGHT ACTIONS: In retrospect, I feel I did a few things wrong and a bunch of things right handling the in-flight portion of my emergency. My biggest mistake was mint turning off tine plaster before impact. I should have. My biggest correct action was not eves a concious one. Both the military and FAA part 121 operations require seat belts and shoulder harness to be worn by flight crew for all takoffs and landings. My habit is to always keep them both on. I loosen, out never remove, the harness only once in a great while at high altitude cruise. Had I not had a tight seat belt and shoulder harness, I would be dead! Instead I walked away from a pretty spectacular crash literally without a scratch.
Other "right actions": My immediate turn towards shore at the first hint of trouble. 2. My immediate raising of the gear. 3. My immediate switch to the header tank which 4. allowed the rapid, and correct, decision that the engine wasnt coming back: this prevented me from wasting precious energy/altitude on keeping the prop windmilling. 5. My rapid attaining of best glide speed for my airplane as determined by flight test. 6. I picked out the only field that I was certain I could make and never let it out of my sight. Remember, I cleared the trees by only 20 feet from almost 2 miles away. Had I omitted any one of the above actions, I probably would have hit the trees or lake. Cornfields are rough on airplanes, but not nearly as rough as trees or water at high speed.
Some additional right actions: I devoted my full attention toward stabilizing the situation before giving any thought to a radio call, I also got the aircraft as slow as I had been able to demonstrate good control in flight test before touchdown. Another very important action was the re-lowering of the nose gear before touch down. Judging from the damage to the gear doors and paint abrasion on the strut, grass drag (=slow down help) on the strut was significant. Had it not been down, I probably would have gone over at 50 mph vs. 20 mph.
My last correct decision was to leave my seat belt buckled when the 160 lb. fireman said "OK, unbuckle the belt". About 15 people had lifted the airplane, still inverted, about 5 feet off the ground. I said to him, "Are you ready to have 215 lb. come tumbling down on your head as soon as I open it?" He said, "wait a minute", and got another fireman to help. I could just see me surviving the crash unscathed only to break my neck in the rescue!
SOME FINAL THOUGHTS: Thanks Burt, for designing a super strong airframe and especially a super strong rollover structure. Without it I would have been severely injured or worse. The TV newsman asked if I was scared. I told him that I was too busy doing my job, flying the airplane, to be scared. Every military flight manual Ive ever used has virtually the same basic instructions for handling any emergency:
1. Maintain aircraft control
2. Analyze the situation
3. Take corrective action.
Nowhere does it say to wring your hands, go berserk yelling for help on the radio, or to contemplate your navel. The only person who can help you out of your hard spot is you, and you wont be any good whatsoever to you if you dont keep a calm, clear mind and concentrate on the business at hand.