The owner of the float-equipped Maule saw it crash. He was there to watch as his friend and a passenger arrived in the airplane. “I witnessed the airplane fly over the field,” he wrote, “and enter a downwind for a landing on Runway 4. As the plane turned from base to final, it banked at a very steep angle (est 75 degrees) and then continued to bank even steeper then went vertical from 50-60 feet altitude and within a second impacted, exploded and burned.”
The 42-year-old, 1,300-hour commercial pilot and his longtime girlfriend both perished in the accident, which the National Transportation Safety Board attributed to “the pilot’s inadequate airspeed and excessive bank angle while maneuvering for landing, which resulted in an aerodynamic stall.”
The scenario of the stall-spin while maneuvering in the traffic pattern is a classic one. It is, and has always been, so common that Leighton Collins devoted many pages to dissecting it in the chapter on “The Dangers of the Air” that he contributed to Stick and Rudder, Wolfgang Langewiesche’s ageless 1944 book on the art of flying. Collins gave a lot of attention to the misuse of the rudder, a control that played a larger role in 1944 than it does today. The rudder may or may not have had anything to do with the fate of this particular Maule — the GPS, which stores altitude, speed and ground track, does not, of course, reveal whether or not an airplane is in coordinated flight — but the mere shape of the ground track, and the testimony of several witnesses, provides sufficient evidence of the sequence of causes that led to the accident.
The pilot had approached the area from the east, first overflying the 2,000-foot turf runway and continuing some distance past it. He then turned back, crossing midfield, and making a left 270 onto the downwind leg. The second, west-to-east crossing of the field was at 860 feet above the ground, but the Maule began descending during the turn to the downwind. By the time it was established on the downwind leg, it was at just 310 feet agl.
Since a traffic pattern is normally flown at 1,000 feet above the runway, a pilot becomes accustomed to a certain relationship between wing, horizon and runway on the downwind leg: The line of sight from airplane to runway is so-and-so many degrees below the horizontal. If the airplane is very low on the downwind, an attempt to maintain that accustomed angle, or anything close to it, results in a downwind leg much closer to the runway than normal.
Regardless of altitude, however, the airplane will require the same amount of room to make the turns from downwind to final. When the Maule passed the approach end of Runway 4, it was about 700 feet laterally from the centerline. Its published stalling speed with full flap is 45 knots, which sounds conservative for an airplane with a gross-weight wing loading of less than 15 pounds per square foot. Assuming a pattern speed of 1.3 times the stalling speed — 59 knots — and 30-degree banked turns, a semicircular turn from downwind to final would require a little more than 1,000 feet. If you spent 10 seconds wings-level on base checking for traffic, your complete turn from downwind to final would use up 2,000 feet — about three times the space the pilot had given himself.
The witness report of a 75-degree bank angle prior to the stall has to be viewed skeptically. It’s difficult to judge the bank angle of a turning airplane, and 75 degrees is practically indistinguishable from vertical. It would be sufficient for an airplane to bank 45 degrees in the traffic pattern for it to look very steeply banked indeed.
According to the GPS record, the pilot began the downwind leg with a groundspeed of 48 knots. Of course, groundspeed and airspeed are not the same thing, but the fact that the downwind groundspeed was very close to the stalling speed implies that there cannot have been much wind.
From the last bit of the GPS record, it appears that the groundspeed as the pilot began his turn from downwind to final was 53 knots. During the first five seconds of the turn, however, his groundspeed dropped from 53 to 44 knots. With essentially no margin above stalling speed, the pilot could not bank more than a few degrees without beginning to lose some of the meager altitude that he still had.
The NTSB report quotes the FAA’s Airplane Flying Handbook as stating that “ … the steeper the angle of bank, the higher the airspeed at which the airplane stalls.” This statement is poorly phrased and could produce a good deal of confusion, as it omits any mention of G loading. In fact, an airplane can be very steeply banked — vertically, in fact — at very low airspeed and still not stall; this is the case at the top of a wingover. The claimed association between speed, bank angle and stall applies only when you are maintaining altitude, and so you have to pull some G to compensate for the tilt of the lift vector. Stalling is always a matter of angle of attack, not of speed or bank angle.
In this case, the pilot does appear to have tried to maintain altitude in a too-steeply banked turn. This required increasing his angle of attack, but he evidently did not increase power at the same time; the decay of groundspeed from 53 to 44 knots most likely reflects induced drag increasing with angle of attack. At a certain point, probably fairly early in the turn, the wing began to stall.
I have not flown a Maule, but I doubt that it stalls abruptly. An abrupt stall would be inconsistent with the philosophy of a STOL design. I suspect that the stall gives ample warning and advances over a range of several knots. If, at the first indication of a stall, the pilot gets the nose down and levels the wings, he could almost certainly recover with little loss of altitude.
So we come to the question of how the pilot in fact reacted to the stall. Obviously, he failed to recover. But to illuminate why he failed to recover, the NTSB found its way to an instructor who had attempted to check the pilot out in a Columbia 350 — the airplane that would become more familiar as the Cessna Corvalis — nine months before the accident. This instructor kept a remarkably detailed and conscientious record of his experiences. If you’re interested in seeing it, you can find it here.
In essence, the instructor observed traits in the pilot — a charismatic and much-admired fellow — that seem to foreshadow the eventual accident. He was always behind the airplane; he was casual about speed control and generally contemptuous of procedures and requirements; he made 45-degree banked turns in the traffic pattern and could not or would not maintain the pattern altitude; he failed to take appropriate action to recover from an impending stall on final approach. On their last landing together, he stalled the airplane, at night, at a height the instructor estimated as 6 to 10 feet. The resulting jolt was such that the instructor believed it had given him a concussion, and he called the owner of the airplane to recommend that the landing gear be inspected before further flight. After that, the pilot, who, one senses, may have found this particular instructor too finicky for his taste, put an end to their work together, probably to the instructor’s great relief.
The instructor’s very vivid account, in juxtaposition with the fatal accident, makes one wonder how a pilot said to be prone to such basic mistakes managed to live as long as he did, pass repeated biennials, and acquire his ratings, which included single- and multiengine land, single-engine sea, and instrument. Satisfied to have found an instructor who identified glaring weaknesses in the pilot’s technique, the NTSB did not seek out the instructors and examiners who had evidently found his skills and attitude acceptable. Too bad; it would have been interesting to hear what they had to say.
_This article is based on the NTSB’s report of the accident and is intended to bring the issues raised to our readers’ attention. It is not intended to judge or to reach any definitive conclusions about the ability or capacity of any person, living or dead, or any aircraft or accessory. _
We welcome your comments on flyingmag.com. In order to maintain a respectful environment, we ask that all comments be on-topic, respectful and spam-free. All comments made here are public and may be republished by Flying.
