A half dozen accidents involving Piper Aircraft Inc. planes with steering difficulties prompted U.S. crash investigators to get involved.

The National Transportation Safety Board (NTSB) probe focuses on six incidents between December 2019 and January 2021. In those accidents, pilots of high-end Piper M600 aircraft had trouble with directional control while landing. Pilots in some of these accidents were concerned about potential issues with nose wheels.

All the planes were damaged after touching down on the runway. No fatalities or serious injuries were reported.

Some pilots involved in the accidents have gathered together and are pushing for government action. They say the common link seems to be a nose-gear problem. The touchdowns were otherwise normal, but the nose-gear misbehaved, causing planes to veer from the runway center. Pedals control the steering and the plane’s rudder, a vertical tail panel.

In two accidents, attempts to control the direction of the nose failed. The planes drove off the strip, seriously damaging the planes. Both planes had to be scrapped. These aircraft can cost $3.5 million each.

Piper, maker of propeller-powered planes since 1937, has issued service bulletins to owners citing the need for maintaining proper front tire pressure and stepped-up inspections. They have also suggested replacement parts for the nose gear and adjustments to be made. Piper M600 owners want more explanations and data. People in the know say the Federal Aviation Administration (FAA) is considering issuing mandatory safety directives.

An NTSB spokesman said, “We have not identified a single common issue present” in all events. Three board staffers are investigating, including a metallurgist. There is no information about how long the probe will continue.

In a letter to M600 owners dated February 4, Piper said the company was “reviewing some landing excursions with the 158 M600 fleet now operating world-wide.” The letter also noted again the importance of maintaining tire pressure and told owners that Piper had previously urged inspections or adjustments of nose-gear components “through an abundance of caution.”

Less than a week later, Piper sent another missive with the words “Piper considers compliance mandatory” across the top. This time the company called for further inspections and sometimes replacement of a key portion of the steering assembly with a “new, improved replacement assembly.” These changes were to be made within the next 50 hours of flight time.

Andrew Lourake, a retired Air Force pilot, had a runway accident in Titusville, FL, in July 2020 after landing an almost new M600. In an interview, he said, “New planes aren’t supposed to do this.” He also said that “if experienced pilots can’t keep them on the runway,” investigators need to figure out what the steering problems are.

The NTSB hasn’t finished Lourake’s accident report yet. Lourake told the safety board that touchdown was normal, but the plane jerked sharply right and wouldn’t respond to his commands. In a preliminary report, it was noted that the NTSB did not travel to the scene of Lourake’s accident. However, an FAA inspector noted three skid marks on the runway, the darkest of which was consistent with the nose landing gear tire.

The report goes on to say that after the nose wheel touched down and pulled right, Lourake applied left rudder and brake inputs to correct, but the plane didn’t respond. The plane stopped in the grass 100’ off the runway.

Another accident took place on Jan. 19, 2021, at the Manchester-Boston Regional Airport that resulted in substantial aircraft damage.

The latest single-engine M600s have a safety feature that can, in an emergency, take over and land a plane automatically. This emergency system does not seem to have any connection to the accidents.

The number of accidents involving private and business planes in the U.S. has remained at approximately four per day, or 1,200 annually, for several years.