Wrestling with the FMC
I read your article entitled "Bad Figures, Dangerous Results" (April 2004, page 51). The continuing occurrences of tail strikes due to bad data in the flight management computer (FMC) are an example of poor system integration and design. The same type of event occurred at my company (except on landing) with the same results. The cause? A zero fuel weight was entered into the FMC that was below the empty weight of the aircraft. We were lucky. No one was injured.
Timothy Crowch is correct in his opinion of man-machine interface. The current method by which a pilot "converses" with the FMC is abysmal. With our fleet, flight plans are inputted into the FMC in a completely illogical manner. The pilot must dance around the multifunction control display unit (MCDU) like a jumping bean. Unrelated data is inputted using function keys along both sides of the screen at the same time.
I remember the first time I saw the complete system (FMC, autopilot, display units, etc.) in a simulator. I asked why the flight plans were inputted in such a haphazard manner. The response was simply, "it’s always been done that way."
Of the incidents I’ve read about involving erroneous FMC data, the flight crew invariably failed to recognize the unreasonable information being displayed. One aspect of the problem is complacency. The longer one goes between incidents, the more complacent one becomes. Another aspect is that of the operator culture, in which the junior crewmembers feel compelled to never question the captain.
There should be more standardization in how advanced FMC systems are integrated. But there first needs to be a paradigm shift in how the user interfaces with the systems. Just as maintenance documentation must now be written to the lowest common denominator, the same approach is needed for the cockpit.
Chris Nichols
Avionics/Systems Engineer
AirTran Airways
Orlando, Fla.
UAV Collision Avoidance
The article in the March issue, "UAVs-Out of Uniform" (page 40) reflects the increasing interest in useful commercial applications for unmanned air vehicles. In the future some UAVs probably will operate in areas currently populated by civil aircraft, such as busy airports.
Working in proximity to civil aircraft will require a collision avoidance capability. NASA is working on collision avoidance systems for "non-cooperative" aircraft, which, I believe, will be a requirement for future systems. Currently, the traffic alert collision avoidance system (TCAS) is the only system that meets U.S. and international requirements for collision avoidance. While TCAS performs its intended function well, it does so against aircraft that are equipped with an operating transponder or another TCAS system. Other systems have been proposed, but they only work with cooperative aircraft. A true collision avoidance system for the future should deal with uncooperative aircraft.
Robert H. Passman
Silver Spring, MD
U.S. in Decline?
Regarding the April 2004 Safety column titled "Bad Figures, Dangerous Results" , in the old, old days we had a one-page chart that gave us gross weight, temperature, airport elevation and bingo takeoff speed. (We called it takeoff speed, not that fancy V1 and other Vs.) We all knew we had about a 15 percent margin, and it worked. Now it has been made complicated, even though aerodynamics has not changed. It’s still an airplane.
Regarding your Editor’s Note in the same issue titled "U.S. Following Europe’s Lead." We always have! Look at the innovations that have come out of Europe since the Wright Brothers, who incidentally may not have been the first to make powered flight, only the first to get widespread publicity. The innovations include metal aircraft, jet engine, jet fighter and bomber, commercial jet, tail-mounted twin jet, tri-jet, twin widebody, swept wing, delta wing, rocket-powered aircraft, fly by wire, ballistic missile, cruise missile, object in space, radar, ILS and autoland. The U.S. adopted these innovations and was able to become dominant because of its market economies of scale and restrictions placed upon Germany after WW II.
With the establishment of the European Union creating a larger market than the U.S. and with other nations such as China and India seeking technological independence, coupled with the self-imposed lack of U.S. innovations, the U.S. is destined to become an also-ran and face a gradual decline in its ability to compete on an intellectual and technological level.
Karl Kettler
Flemington, N.J.