Story updated on 4 April with comments in paragraph seven from the FAA and Boeing.
The US National Transportation Safety Board (NTSB) has issued recommendations aimed at preventing hard landings in Boeing MD-11 aircraft.
The recommendations follow investigations by the NTSB into a series of MD-11 hard landings in recent years that resulted in total hull loss, say documents released by the agency.
The recommendations include a call for the US Federal Aviation Administration (FAA) and Boeing to work together to study the possibility of equipping MD-11s with flare cueing systems and weight-on-wheels cueing systems.
The safety agency says flare cueing systems could potentially help pilots make correct control inputs during landing, while weight-on-wheels systems could help ensure pilots react properly when the aircraft bounces during landing, say the NTSB documents, dated 2 April.
In addition, the FAA and Boeing should evaluate the effect of brief engine power surges on MD-11 landing distances, and provide operators with adjusted landing distance figures.
The NTSB also suggests that the FAA reconvene a panel to determine if flight currency requirements for MD-11 pilots should be modified.
The FAA tells Flightglobal it will "carefully consider" the NTSB's recommendations and respond within 90 days, as required. Boeing says it is reviewing the recommendations, but declined further comment.
There were at least 13 MD-11 hard landings between 1994 and 2010, some of which killed crew and passengers. Incidents include a China Airlines aircraft in 1999, FedEx aircraft in 1997 and 2009, and a Lufthansa aircraft in 2010, says the NTSB.
MD-11s have the highest rate of hard landings among 27 Western-built types, says the agency.
Pilots of accident aircraft frequently made late or ineffective flares during landing, or mismanaged bouncing, causing the aircraft to porpoise, which can fracture the MD-11s main wing spare and cause the aircraft to roll over, says the NTSB.
Other factors contributing to the accidents include the MD-11s relatively high landing airspeed, which can make timing a flare more difficult for pilots.
Also, the aircrafts cockpit is far ahead of its centre of gravity, which can result misleading motion cues that hinder pilots ability to determine if the landing gear contacted the ground, says the NTSB.
That factor is exacerbated because the MD-11, a derivative of the earlier DC-10, has a 100in extension forward of the wings.
Also, the MD-11s systems automatically reduce thrust during a flare, a feature that can delay pilots ability to adjust thrust if the sink rate becomes excessive, says the NTSB.
The agency also notes that pilots who fly the medium- to long-range aircraft do not perform as many landings as those who fly shorter-range aircraft.
It recommends that the FAA examine whether MD-11 pilots should be required to perform more than the currently-required three landings every 90 days.