Spoiled by the spoiler.
As the aircraft accelerated and angle of attack (AOA) was reduced, the aircraft became progressively harder to control and needed increasing right stick and rudder to maintain near-wings-level flight. The uncommanded left turn continued with increasing left angle of bank despite the pilot's applying full counter-control inputs.
At 240 knots, as the aircraft reached the 135-degree point during the downwind turn, the Tomcat continued to roll left through 100-degree angle of bank. The pilot then initiated ejection. The aircraft crashed and was destroyed but the pilot and RIO were not injured.
Grampaw Pettibone says:
Close call. It's as scary as it gets when you're down low and the bird wants to tip over despite maximum effort to keep it upright.
In this accident, investigators learned the spoiler actuator was corroded, resulting in the inadvertent and unexpected extension of the spoiler. Apart from exceeding the 225-knot airspeed limitation while in the landing configuration, the crew did well. The Tomcat might have handled a little better if they'd slowed down from 240 knots.
The investigators acquired new knowledge about the Tomcat from this accident. For example, wind tunnel testing after the mishap revealed a previously unidentified aerodynamic force: in one-G flight with flaps down configuration, the true AOA is negative when above 180 knots. In the negative AOA region, dihedral effect (roll due to sideslip) reverses. Right rudder inputs which normally result in right roll produce anywhere from no-roll moment to left-roll moment, depending on the AOA.
Anyway, regardless of the technicalities of 21st century aviation, the time-tested axiom--expect the unexpected--still applies. It's tough to honor this principle every minute of a sortie, but it's helpful to remember it when launching and recovering from shore or sea.
Gramps from Yesteryear
Illustrations by Ted Wilbur
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||Grampaw Pettibone|
|Publication:||Naval Aviation News|
|Date:||May 1, 2004|
|Previous Article:||ANA photo contest.|
|Next Article:||Fly by wire.|
|Up and At 'Em.|
|Tail-first touchdown. (Grampaw Pettibone).|
|Trouble in a Turbo-Mentor.|
|Gramps from yesteryear.|
|Shucks and flashlights.|
|Fly by wire.|