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When Smoke Causes a Fire

Knowing an airplane’s flying characteristics

BY J. MAC MCCLELLAN

AN OPERATING CONTROL TOWER provides many benefits to pilots. Controllers, of course, separate airplanes on the runway and direct taxiing airplanes to avoid conflicts. The controllers also provide you with IFR clearances, or handoffs for radar advisories. The people in the tower also can pass along pilot reports warning of us of wind shear on final that other pilots experienced, or to be alert for poor braking conditions or other runway hazards.

And tower controllers also keep an eye on airplanes departing and arriving and are in the best position to issue a timely warning if they see something wrong that the pilot may not be aware of. And that’s what an attentive tower controller did when he saw smoke trailing a Lancair IV-P just as the landing gear was retracting after takeoff. The controller radioed the Lancair pilot telling him of the smoke, but nobody from the Lancair responded.

Almost immediately after the controller warned the Lancair of the trailing smoke, witnesses saw the super high performance homebuilt pull up into an abrupt climbing left turn, perhaps initiating a return to the runway. As the Lancair nosed up and banked, the witnesses also reported that the wings rocked back and forth. The airplane then went into a near vertical descent crashing into an orange grove. The airplane exploded on impact, and witnesses reported there was a huge fireball. All three people in the Lancair were killed instantly.

Based on witness reports of the flight path and behavior of the Lancair, the NTSB reached the obvious finding that the “pilot’s failure to maintain an adequate airspeed during climb-out resulting in an aerodynamic stall/spin” was the probable cause of the accident.

The composite airframe of the Lancair was destroyed on impact, and the post-crash fire made analysis of the wreckage by the NTSB almost impossible. The Board did determine that all control surfaces were accounted for at the accident site, but control system continuity could not be established.

The NTSB couldn’t find any pre-crash abnormalities with the engine or the airframe. And it could not determine a source of the smoke the tower controller saw trailing the airplane on takeoff.

Why would a pilot pull a normally functioning airplane that is taking off in benign weather conditions up into a stall resulting in an unrecoverable spin? The NTSB does not attempt to answer that question.

The Lancair IV-P had accumulated 998.7 hours when its altimeter and transponder were checked five days before the accident. That was the last available airplane log entry. The conditional inspection had been conducted about six weeks before the accident, and there were no unresolved maintenance discrepancies.

The Continental TSIO-550-E turbocharged engine had been in the Lancair since it was built and had the same total time as the airframe.

The owner of the airplane was recovered from the left front seat. The NTSB calls this person the “pilot-rated passenger/ owner.” The person the NTSB calls the pilot was in the right front seat. The Lancair was departing on an IFR clearance, and perhaps the right-seat pilot had been listed as pilot in command on the flight plan and that’s how the NTSB determined he was the pilot. The pilot-rated passenger/ owner had a private certificate with single and multiengine ratings, but no instrument rating, so that would appear to indicate that the right seat pilot had to legally be PIC for the IFR flight.

Both pilots were 27 years old. The Lancair owner had hired the right-seat pilot about 10 months earlier to be his company pilot. The right-seat pilot had commercial and CFI certificates, with instrument rating. The Board could not locate a personal logbook for the pilot, but about five months earlier on his application for a second-class medical he listed 600 hours of total time, with 200 hours logged in the preceding six months.

The right-seat pilot reported on an insurance application that was submitted about six weeks before the accident that he had completed initial training in the Lancair IV-P. The NTSB report does not say where he attended training, but notes that he logged 9.4 flight hours during the course and received a high altitude endorsement. Aircraft logs showed the pilot had then flown the accident airplane a total of 20.5 hours before the crash.

The passenger/owner pilot’s personal logbook could not be located either, but on his third-class medical application made about two and a half years before the accident, he reported 60 hours’ total time, with 30 hours in the preceding six months.

LANCAIR PERFORMANCE

The Lancair IV-P is one of the fastest piston singles in existence with a 280 knot cruise speed (330 mph is the number the company publishes) at 24,000 feet. The airplane is very sleek, but much of its high speed is due to the 350 or so horsepower the turbocharged Continental engine can produce at 24,000 feet, and the very small size of the wing.

There is an old saw that airplanes take off and climb on wing area, but cruise on wing span. That means you want a large wing to fly slowly for takeoff and initial climb, but a very small wing area to cut drag in cruise. That apparent contradiction is actually, and routinely, resolved in larger jets that have huge Fowler type wing flaps that track aft to increase wing area markedly. The Lancair IV-P does the same. It has very large Fowler type flaps that, for takeoff, track fully aft before then descending 10 degrees to add wing area as well as camber to the small wing.

According to Lancair’s published specs, the design maximum takeoff weight for the IV-P is 3,550 pounds, and the gross wing area with flaps retracted is only 98 square feet. Conventional piston singles such as the Beech A36 Bonanza and the Cessna 210 have maximum takeoff weights of about the same value, but the wing area on those airplanes is approximately 175 square feet, 56 percent greater than the Lancair. The wing loading—the weight supported by each square foot of wing area—is around 20 pounds per square foot on the conventional production singles, but is 36 pounds on the Lancair.

Certification rules require single-engine airplanes to stall, in the landing configuration, no faster than 61 knots. This standard was established when the CAR 3 rules were formulated about 70 years ago. Most production piston singles actually stall a few knots below the 61 knot limit, but a few such as the Cirrus SR22 and the Cessna pressurized P210 bump right up against the limit. The P210’s faster stall is a result of its

4,000 pound maximum takeoff weight, while the Cirrus stalls at that speed because its wing area is smaller at around 145 square feet.

As proof of how effective the slotted Fowler type flaps on the Lancair IV-P are, the company says that the airplane stalls at about 64 knots with the flaps fully extended. With the optional winglets Lancair says the “dirty”—its word—stall occurs at 73 mph, which equals 62 knots. The company doesn’t specify that those stall speeds are at maximum takeoff weight, which is the industry norm for such specifications, but we can assume that to be true. And, of course, all Lancairs are amateur-built airplanes, so builder modifications or variances could alter the actual stalling speed of any individual IV-P.

FOWLER FLAPS

As you will remember from private pilot ground school, wing flaps increase both available lift and drag. On the Lancair the Fowler type flaps track aft emerging from the trailing edge of the wing to add total wing area. The flaps then extend trailing edge down, and a slot is opened between the trailing edge of the wing and the leading edge of the flaps. This slot encourages airflow to remain attached to the upper surface of the flap, which adds lift-producing efficiency to the extended flap. You can see this type of flap design on any jet liner that also needs to reconfigure a small wing suited for high speed, high altitude cruise, to a wing that can fly slowly enough for reasonable takeoff and landing speeds.

But even the extremely effective slotted Fowler type flap cannot avoid a large increase in drag. In jets the drag is actually useful because turbine engines can only be throttled down so far and continue to produce considerable thrust at flight idle. Without the drag of large flaps it would be difficult for a jet to approach for landing at any reasonable speed. Jet pilots, however, are trained to maintain a target airspeed well above stall, and also to keep engine power up to prevent the drag created by the flaps from leading to rapid decay of airspeed and loss of altitude.

Another propeller airplane that uses very large slotted Fowler type flaps to reduce takeoff and landing speeds but retain a small wing area for high speed cruise is the Mitsubishi MU-2 twin turboprops. The big flap on the MU-2 is very effective, but also generates more drag than found on a typical propeller twin. The MU-2 has had a controversial safety record over the years, but a very rigid and detailed initial and recurrent training requirement the FAA imposed on MU-2 pilots about five years ago appears to have resolved the problem. Even the most ardent MU-2 fan must admit that the airplane behaves differently than other piston and turboprop twins, and the training requirement addresses the differences and teaches pilots how to operate the airplane within its design limits.

Like the MU-2, the Lancair IV-P is fundamentally different from the huge majority of propeller singles. There is no FAA requirement for specialized and specific training in the Lancair, but such courses have been established and are popular with airplane owners, and even more popular with their insurance companies.

The pilot in command of the accident Lancair had received type-specific training in the airplane and should have been aware of the flying characteristics of the small wing and large flaps. Why one of the pilots—nobody knows for sure who was manipulating the controls—in the Lancair would both raise the nose and enter a steep bank at a low airspeed with takeoff flaps extended is impossible to know. Perhaps an airplane of larger wing area and lower drag flaps may have continued to fly through such a maneuver. The NTSB doesn’t speculate. But in aerodynamics there is no free lunch. Large effective flaps do add low speed lift and perform that function thousands of times a day each time a jet takes off and lands. But the drag those flaps demand in return for producing lift never goes away, and pilots who fly airplanes with small wing area and large flaps must always account for that characteristic.

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.

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