EAA Sport Aviation - October 2011

Upcoming Workshops

Oct. 15-16 • Oshkosh, WI Repairman (LSA) Inspection – Airplane

Oct. 22-23 • Griffin, GA TIG Welding

Oct. 22-23 • Frederick, MD Van’s RV Assembly

Oct. 29-30 • Columbus, OH Composite Construction, Electrical Systems, Fabric Covering, Gas Welding, Sheet Metal & What’s Involved in Kitbuilding

Nov. 5-6 • Duluth, GA Composite Construction, Electrical Systems, Fabric Covering, Sheet Metal & What’s Involved in Kitbuilding

Nov. 19-20 • Riverside, CA Composite Construction, Electrical Systems, Fabric Covering, Sheet Metal & What’s Involved in Kitbuilding

Dec. 10-11 • Houston, TX Composite Construction, Electrical Systems, Fabric Covering, Gas Welding, Sheet Metal & What’s Involved in Kitbuilding See the complete list of all our workshops at SportAir.org/workshops/index.html

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airspeed, groundspeed, rate of climb, g-loading, corrected wind speed, corrected wind direction, air temperature, density altitude, fuel total quantity, engine rpm, fuel flow, and other engine performance parameters once each second.

The recovered data records showed that about five minutes and 35 seconds before the end of the recording the Lancair flew into significant continuous turbulence with g-loading excursions from 0.77g to 1.5g. After about four and a half minutes of flying in the turbulence and clouds, the pilot lost control. The Lancair entered a 30-degree bank to the right and began descending at 600 to 900 fpm. Engine power parameters remained constant.

About 25 seconds before the end of the recording the Lancair was flying at 10,500 feet, and the bank angle increased to near 100 degrees and the rate of descent went from 1,000 fpm to an astonishing 11,500 fpm. The indicated airspeed jumped from about 150 knots to 280 knots. Throughout this extreme loss of control the g-loading remained constant at 1.1g.

The final six seconds of recorded data show the Lancair loading increasing rapidly to 4.8g. The last data point shows the airplane at 6,135 feet, 88. 6 degrees nose-down, a 113-degree angle of bank, and an indicated airspeed of 290 knots. Throughout the entire event engine rpm remained constant at 2400 and fuel flow was steady at 11. 8 to 12.0 gph.

The wreckage of the composite airframe Lancair was found spread over a half-mile area. The breakup was consistent with the pilot exiting the bottom of the clouds and then overloading the airplane in an attempt to recover from the extremely unusual attitude. The last g-loading recorded was 4.8g. The NTSB did not report any design or construction flaws in the airplane.

The only abnormal item found in the wreckage was the elevator control rod that linked the cockpit control to the elevator surface. This “elevator torque tube” showed evidence that only “ 2-3 threads” were engaged in the fitting on one end, while the threads were fully engaged on the other end of the tube. This was contrary to instructions in the Lancair ES builder’s guide that provides specific measurement for how far the rod end should be screwed in.

The real lesson here is how hard
it can be to control a small air-
plane while flying in significant
turbulence in IMC conditions.

In the end the NTSB did not find that
the elevator push rod contributed to the
accident. The official probable cause of the
accident is “the pilot’s failure to maintain
control while in cruise flight due to spatial
disorientation.” The board added that
“contributing to the accident was turbu-
lence and clouds.”
The probable cause is merely stating
the obvious. But the real lesson here is how
hard it can be to control a small airplane
while flying in significant turbulence in
IMC conditions. The g-loadings recorded
before the Lancair pilot lost control show
the airplane was being tossed around vig-
orously making control difficult. Once he
allowed the airplane to enter a steep bank
it wrapped up into a spiral dive that allows
almost unbelievable airspeeds and descent
rates to develop. Recovery from a fully
developed spiral dive without exceeding
the structural limits of an airplane can be
almost impossible because control inputs
would have to be so gradual that not
enough altitude is available.

The reminder for us all is that tall mountains can generate turbulence strong enough to threaten the safety of any airplane or pilot when the wind at ridge level is strong. Staying out of clouds downwind of high mountains won’t guarantee a smooth ride, but clear air does greatly improve any pilot’s chances of keeping the airplane under control and out of the worst turbulence.

This article is based solely on the official final NTSB report of the accident and is intended to bring reader’s attention to the issues raised in the report. It is not intended to judge or reach any definitive conclusions about the ability or capacity of any person, living or dead, or any aircraft or accessory.