Figure: N777TY, from Airliners.net

Eddie Sez:

According to the accident report this mishap was caused by by mechanics who forgot to remove popsicle sticks used during routine maintenance and by Gulfstream who should have had a better method to disable the weight on wheel switches.

Those points are true, but they didn't cause the mishap. The mishap was caused by pilots who failed to perform a complete external preflight, failed to correctly analyze clearly presented crew alerting system warnings, and failed to execute the proper emergency procedure checklists. Additionally, they failed to take advantage of several commonly accepted techniques, any one of which would have prevented this aircraft from being destroyed.

In the words of the captain, these pilots "blew it." I think they did. But I'm not sure they were bad pilots, they made it to the premier jet in corporate aviation. There weren't many GV pilots in 2002 and they had to be of a special cut to make it to that jet. But even the best pilots can become complacent and complacency shows at every phase of this mishap. I think there are several lessons here for all pilots, Gulfstream or not:

  • We often rush the external preflight because we almost never find anything wrong with the airplane. As we become more and more complacent we drop more and more items from our internal list of things to worry about. You should accomplish the external preflight with checklist in hand, every month or so, just to remind yourself of what you might be missing. You should certainly do this for every external preflight following maintenance.

  • The "old heads," who have been flying the airplane longer than you, often adopt catching phrases or call outs as a way of preventing these kinds of incidents from happening. If you adopt these call outs, you need to understand why. Many GV series pilots, myself included, always state "three green, four in the air" prior to arming the ground spoilers. It isn't clear if these pilots used the call out. If they didn't, it could have save them. If they did, they forgot the reason behind it.

  • The CAS messages are color coded for a reason and you shouldn't lightly skip over a red message because you think you know what it means. Also, just because a message is blue and labelled "advisory" doesn't mean it isn't important.

  • We quite often have new technology we don't trust and revert to old procedures and techniques. The GV was the first Gulfstream with autothrottles authorized for landing and they work very well. Some pilots from older Gulfstreams don't like the fact the GV autothrottles perform a gradual power reduction starting at 50 feet and would rather "chop" the power at a higher altitude. It appears these pilots did that. Had they allowed the autothrottles to do their job, I think the landing would not have destroyed the airplane.

What follows are quotes from the sources listed below, as well as my comments in blue.


Accident Report


Narrative

[NTSB Accident Narrative]

    The main landing gear weight on wheel (WOW) switches are switches with a roller on a cam. When the aircraft is airborne the cam rotates to a low point and the switch extends. The mechanic needed both main landing gear WOW switches to be in the ground mode while the aircraft was on jacks so he placed the wooden sticks between the cam and the switch on both gear, forcing it into the "ground mode."

    The wooden sticks did not have warning flags attached. Gulfstream now has purpose-made wedges with large red "Remove before flight" banners.


Probable Cause

[NTSB Accident Summary] The flight crew's failure to follow preflight inspection/checklist procedures, which resulted in their failure to detect wooden sticks in the landing gear weight-on-wheel switches and their failure in flight to respond to crew alert messages to disarm the ground spoilers, which deployed when the crew moved the throttles to idle during the landing flare, causing the airplane to land hard. Contributing to the accident was maintenance personnel's failure to remove the sticks from the weight-on-wheels switches after maintenance was completed.


See Also:


References

http://www.airliners.net

Gulfstream GV Airplane Flight Manual, Revision 30, 13 May 2008

Gulfstream GV Aircraft Operating Manual, GAC-AC-GV-OPS-0002, Revision 30, May 13, 2008

Gulfstream GV Quick Reference Handbook, Revision 30, June 26, 2008

NTSB Aircraft Accident Summary and Narrative, MIA02LA060, Gulfstream G-V, N777TY, February 14, 2002