Tales of the F-14
More recollections of the fabled fighter.
- By airspacemag.com
- Air & Space magazine, September 2006
(Page 2 of 6)
After takeoff we climbed to 10,000 feet, lest there be any hydraulic or mechanical mischief in the system. We had rounded Montauk Point and were headed back along Long Island’s south shore when we got to gear retraction entry on the flight card.
Immediately after raising the gear handle, our A-6 chase pilot said we were venting fluid out of the right side of the airplane. At the same instant, the combined hydraulic system gauge went to zero. Twenty-one gallons of hydraulic fluid had just left the airplane.
We started back to home base at 180 knots, our limit airspeed because the flaps were still extended. In about ten minutes, we were lined up with our runway about three miles out when we blew our gear down with the nitrogen bottle, since our flight hydraulic system only powered the flight controls.
At this time, our chase said we were venting more fluid, and our flight hydraulic system gauge went to zero. The airplane then went through about two cycles of gentle but uncontrollable pitching, and then snapped violently nose down.
At this point we were about a half-mile short of the runway, about 25 feet above the trees. Bill quickly initiated the ejection sequence using his face curtain. A sensitive accelerometer on the nose strut recorded and telemetered back to the ground the little blips showing the firing of the canopy and then the ejection guns on the two seats in turn. That all took 0.9 seconds as advertised; 0.4 seconds later the nosewheel hit a tree!
My Martin-Baker seat sent me staight up about 150 feet, but when Bill’s fired a split second later, it sent him forward, only gaining about 10 feet vertically. Both chutes deployed nicely, and neither of us was injured. Thirty minutes later, when the fire caused by 10,000 pounds of fuel was put out, the ground crew found two fractured 5/16th-inch-inner-diameter titanium hydraulic lines, one in each wheel well.
The F-14 had an all-titanium hydraulic system with an 84-gallon-per-minute pump on each engine with no accumulators, all in the interest of saving weight. Each pump had nine pistons, which were varied in output by a swash plate. As it turned out, each time one of the nine pistons did its thing, it sent a 200-300-pounds-per-square-inch pulse down the basic 3,000-psi system. Apparently, without accumulators to dampen the pulses, a resonance occurred which fatigued the lines. Engineering duplicated the failure on a full-scale mockup of the system in 1.2 minutes at just the right pump RPM. When the line was changed to stainless steel, the line failed in 23 minutes. The answer was not material, but proper forming and clamping of the line to prevent resonance. The second F-14 did not make its first flight until May 24, 1971. There were no hydraulic problems again on the F-14 program.
As an embarrassing postscript, this whole episode could have been avoided if we had not been in such a bloody hurry. During one of the all-night engine runs a few days before First Flight, I was running the engines under the lights during systems check at 2-3 a.m. when the plane captain started waving his arms to shut down the engines. I looked over the side and saw a large puddle of hydraulic fluid.
I asked what happened, and he said it must have been a loose B nut. Well, there was only a handful of B nuts on the airplane, since most of the hydraulic connectors were the super-dry Cryofit connectors. We were all sleepy, so we went home and thought no more about it.