The Wall Street Journal
By Andy Pasztor
Updated February 15, 2021 4:25 pm ET
U.S. crash investigators are examining half a dozen accidents in which private turboprop planes built by Piper Aircraft Inc. experienced difficulties with steering on runways after touchdowns.
The probe by the National Transportation Safety Board, which hasn’t been reported before, focuses on six events between December 2019 and January 2021 in which pilots of high-end Piper M600 aircraft reported loss of directional control while landing, according to a safety-board spokesman. Pilots involved in some of the accidents have expressed concern about potential problems affecting nose wheels.
All of the planes suffered damage after touching down on the runway, according to the NTSB spokesman; no fatalities or serious injuries were reported.
An informal group of M600 pilots involved in the accidents is pushing for government action, arguing the common link appears to be a nose-gear problem during otherwise normal touchdowns, causing the planes to veer from the center of the runway. Steering is controlled through pedals that also move the plane’s rudder, a vertical panel on the tail.
In two of the accidents, aviators at the controls said, efforts to control the direction of the nose failed as they careened off the strip, causing severe damage that resulted in scrapping aircraft that can cost about $3.5 million apiece.
A Piper spokeswoman and a lawyer for the company declined to comment on specifics, citing ongoing safety board investigations.
Based in Vero Beach, Florida, Piper has been producing propeller-powered planes since 1937 and currently markets models for business and personal uses. The manufacturer has been owned and managed by the government of Brunei for a decade.
The company has issued a handful of service bulletins over the past eight months calling for owners to take measures ranging from maintaining proper front tire pressure to stepped-up inspections, adjustments and sometimes replacement of parts affecting the nose gear. Piper M600 owners are demanding further explanations and data, while people familiar with the matter said the Federal Aviation Administration is considering issuing mandatory safety directives.
The NTSB spokesman said investigators were aware of the service bulletins and the replacement-parts issue. “We have not identified a single common issue present” in all the events, he said. The spokesman said three board staffers, including a metallurgist, are participating in the investigation. It isn’t clear how long it will last.
The FAA said it was monitoring the issue and declined to elaborate.
On February 4, Piper sent a letter to M600 owners saying the company was “reviewing some landing excursions with the 158 M600 fleet now operating world-wide.” The letter reiterated the importance of maintaining tire pressure and reminded owners that “through an abundance of caution,” Piper previously had urged inspections or adjustments of various nose-gear components.
Less than a week later, the company issued a service bulletin calling for further inspections and in some instances replacement of a key portion of the steering assembly with a “new, improved replacement assembly.” The replacement was supposed to occur within the next 50 hours of flight time. The top of the bulletin said: “Piper considers compliance mandatory.”
Referring to the so-called runway excursions, Andrew Lourake, a retired Air Force pilot who had a serious runway accident in July after landing an almost brand-new M600 at an airport in Titusville, Fla., said in an interview: “New planes aren’t supposed to do this.”
Investigators need to find answers to M600 steering problems, Mr. Lourake said, “if experienced pilots can’t keep them on the runway.”
The NTSB hasn’t issued a final report on Mr. Lourake’s accident. He told the safety board the nose wheel touched down normally but the plane veered sharply right and didn’t respond to his commands.
The latest single-engine M600 models include a safety feature that can take over a plane and land it automatically in an emergency. The system can manage aircraft speed and engine performance on its own, while computers are designed to communicate with air-traffic controllers, line up with the correct runway and extend landing gear—all without any human input. The emergency system, which Piper has marketed extensively, doesn’t appear to have any connection to the accidents, pilots and safety experts familiar with the matter said.
The investigation comes as the number of accidents involving private and business planes in the United States has remained stable for several years at around 1,200 annually, or nearly four a day.
Full steering deflection is available in the existing design by direct linkage and bellcrank connection to the rudder pedals, making it possible for the nosewheel to be turned too far off center at nose wheel touch.
ReplyDeleteExperienced pilot pedal-centering intentions aside, there will be instances where the nose wheel steering angle is too far off track at touch with the runway. When that is the case, there is skidding and impaired steering results. Swap-steering the nosewheel rapidly to the other direction's limit just continues the skidding action while inertia rules the yaw motion already underway.
Redesign needs to limit available nosewheel steering deflection at high speed. Citation's travel limit of +/- 20 degrees would probably work. Nobody will want to be the first person to say that such a high complexity change and re-certification must be done.
“new, improved replacement assembly.” All we need to know. Hello, Piper lawyers.
ReplyDelete