All - I get quite a few questions on the F-14 via PM or in the threads...I flew the big fighter for 10 years, including in combat, and had 2 instructor tours in it.
I am guessing that a few other folks might be interested in the particulars of the jet, so here's the beginning of the thread...
WINGSWEEP:
The Tomcat's wings were programmed as a function of airspeed and altitude...based on the air data computer (world's first integrated circuit, by the way) and they worked automatically. The pilot could take manual control, via a button on the right throttle, and move them aft of the programmed position, but not forward. If the programmed position was aft of the pilot-selected position, they would go back to automatic mode and continue to move aft.
Moving the wings aft reduced high speed drag, moving them forward increased low speed lift. In particular, the sweep angle of 68 degrees kept the wing tips inside the supersonic shock cone of at speeds up to roughly 2.5 Mach. The airplane had a design criterion of 2.0 Mach dash speed, and it reached 2.3 Mach in development testing, so the 68 degrees sweep was conservative. There wasn't a huge change in area, and the F-14 got some lift from its wide, flat fuselage, particularly at high AOA, but there was a change in center of pressure with aft wing sweep - which resulted in a nose down change in trim as the wings moved aft.
This trim change required big horizontal tails to overcome the pitch trim change at all altitudes/speeds and keep full supersonic maneuverability. The F-111, for example, was only able to pull 2G when it was at full aft sweep and high altitude...the F-14 could pull right to its lift (or G) limit at every speed.
Speaking of speeds, I've seen 850 KIAS in level flight, over 900 KIAS in a descent...there are very few airplanes ever built that could achieve those numbers...the Hornet wouldn't have a prayer of going that fast...(sorry Hornet guys...loved that jet, but it was no speedster...).
TOP GUN "HIT THE BRAKES":
The "hit the brakes" was complete Hollywood. Sure, you could pitch-pulse the airplane (remember those big horizontal tails? They worked really well at low speed), but tactically speaking, you achieved nothing except to point the plane and slow it down...that might defeat a gunshot...it might be worthwhile...but in general, it had no tactical use...and it was certainly no "magic" move...
ENGINE STALLS AND FLAT SPINS:
As far as engine stalls – the TF-30 power plant (intended for the F-111, not a fighter) in the F-14A was prone to them, jet wash would be one cause, but throttle transients, high AOA maneuvering, missile or gun gas ingestion, particularly in combination, could cause a compressor stall. The GE F-110-400 in the F-14B/D was very stall resistant. I’ve had literally dozens of engine compressor stalls in the F-14A…I’ve lost track of all of them…
The engines were 9 feet apart, so, were one engine to stall at low speed (less than 140 KIAS), the plane would experience an uncontrolled yaw. Left unaddressed, that yaw could develop into a spin, particularly if the speed was very low and the AOA was very high. In the event of an engine stall, getting the AOA under control, and getting the throttles to idle (to eliminate the yaw) were critical action items if an engine stalled. Generally, the aircraft was controllable if those steps were taken, even if the engine had to be re-started. Every stall I’ve ever had was fixable in the air – either the engine had to be shut down and re-started or the stall cleared with throttles at idle and restoration of normal inlet air flow.
The flat spin part of the movie was realistic – we lost a lot of F-14s to flat spins. A fully-developed flat spin was considered unrecoverable…some guys were able to correct it in the incipient phase (as it developed…but it only took a second or two to develop) before it was fully developed. A fully developed flat spin resulted in 6+ G forwards in the cockpit (pinning the pilot against the instruments if he hadn’t locked his harness during the loss of control), 170 degrees per second yaw rate, and a descent rate in excess of 30,000 feet per minute…
NASA modified an F-14 to do high AOA testing and investigate the flat spin modes of the F-14 in the 70s. That airplane had a spin recovery parachute added between the tails and a hydrazine back-up hydraulic module installed to provide hydraulic power to the controls if both engines stalled (which generally happened in a fully developed spin). The clarified the above parameter for the spin…but recovery was very difficult…
After several flights, even with the special modifications, the NASA Test Pilots crashed the jet during testing…turns out they couldn’t recover from a spin any better than the fleet pilots…
So...ask away...I'll post my answers here.
Cheers,
Astro
I am guessing that a few other folks might be interested in the particulars of the jet, so here's the beginning of the thread...
WINGSWEEP:
The Tomcat's wings were programmed as a function of airspeed and altitude...based on the air data computer (world's first integrated circuit, by the way) and they worked automatically. The pilot could take manual control, via a button on the right throttle, and move them aft of the programmed position, but not forward. If the programmed position was aft of the pilot-selected position, they would go back to automatic mode and continue to move aft.
Moving the wings aft reduced high speed drag, moving them forward increased low speed lift. In particular, the sweep angle of 68 degrees kept the wing tips inside the supersonic shock cone of at speeds up to roughly 2.5 Mach. The airplane had a design criterion of 2.0 Mach dash speed, and it reached 2.3 Mach in development testing, so the 68 degrees sweep was conservative. There wasn't a huge change in area, and the F-14 got some lift from its wide, flat fuselage, particularly at high AOA, but there was a change in center of pressure with aft wing sweep - which resulted in a nose down change in trim as the wings moved aft.
This trim change required big horizontal tails to overcome the pitch trim change at all altitudes/speeds and keep full supersonic maneuverability. The F-111, for example, was only able to pull 2G when it was at full aft sweep and high altitude...the F-14 could pull right to its lift (or G) limit at every speed.
Speaking of speeds, I've seen 850 KIAS in level flight, over 900 KIAS in a descent...there are very few airplanes ever built that could achieve those numbers...the Hornet wouldn't have a prayer of going that fast...(sorry Hornet guys...loved that jet, but it was no speedster...).
TOP GUN "HIT THE BRAKES":
The "hit the brakes" was complete Hollywood. Sure, you could pitch-pulse the airplane (remember those big horizontal tails? They worked really well at low speed), but tactically speaking, you achieved nothing except to point the plane and slow it down...that might defeat a gunshot...it might be worthwhile...but in general, it had no tactical use...and it was certainly no "magic" move...
ENGINE STALLS AND FLAT SPINS:
As far as engine stalls – the TF-30 power plant (intended for the F-111, not a fighter) in the F-14A was prone to them, jet wash would be one cause, but throttle transients, high AOA maneuvering, missile or gun gas ingestion, particularly in combination, could cause a compressor stall. The GE F-110-400 in the F-14B/D was very stall resistant. I’ve had literally dozens of engine compressor stalls in the F-14A…I’ve lost track of all of them…
The engines were 9 feet apart, so, were one engine to stall at low speed (less than 140 KIAS), the plane would experience an uncontrolled yaw. Left unaddressed, that yaw could develop into a spin, particularly if the speed was very low and the AOA was very high. In the event of an engine stall, getting the AOA under control, and getting the throttles to idle (to eliminate the yaw) were critical action items if an engine stalled. Generally, the aircraft was controllable if those steps were taken, even if the engine had to be re-started. Every stall I’ve ever had was fixable in the air – either the engine had to be shut down and re-started or the stall cleared with throttles at idle and restoration of normal inlet air flow.
The flat spin part of the movie was realistic – we lost a lot of F-14s to flat spins. A fully-developed flat spin was considered unrecoverable…some guys were able to correct it in the incipient phase (as it developed…but it only took a second or two to develop) before it was fully developed. A fully developed flat spin resulted in 6+ G forwards in the cockpit (pinning the pilot against the instruments if he hadn’t locked his harness during the loss of control), 170 degrees per second yaw rate, and a descent rate in excess of 30,000 feet per minute…
NASA modified an F-14 to do high AOA testing and investigate the flat spin modes of the F-14 in the 70s. That airplane had a spin recovery parachute added between the tails and a hydrazine back-up hydraulic module installed to provide hydraulic power to the controls if both engines stalled (which generally happened in a fully developed spin). The clarified the above parameter for the spin…but recovery was very difficult…
After several flights, even with the special modifications, the NASA Test Pilots crashed the jet during testing…turns out they couldn’t recover from a spin any better than the fleet pilots…
So...ask away...I'll post my answers here.
Cheers,
Astro
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