militaryaircraft

The original Tomcat engine, the Pratt & Whitney TF30 had the propensity to cause stalls/spins as a result of airflow-induced engine stalls

The impressive video in this post shows F-14A crewmembers ejecting from their Tomcat after flat spin testing went wrong.

According to former F-14 Tomcat pilot Gregory Quist’s comment to the video “The test center had deemed Tomcat un-spinnable when I went through training in 1975-76. We as students were instructed to try and spin on one of our lesson flights. . Couldn’t spin the jet no matter how hard one tried. Only a nose-down high buffet fully controllable spiral evolved in such attempts. I was told this test crew in this test ground camera video, after their normal test flight, decided they had extra gas to go to a higher altitude and try this unplanned (since Tomcat “couldn’t be spun’ by PAX test center). The thinner air allowed it to spin. […] I heard they got in a little trouble for doing things unplanned. Anyway, that was the scuttlebutt at the time whether true or not.”

Noteworthy the troubles with the original Tomcat engine, the Pratt & Whitney TF30 were well-publicized because of their propensity to cause stalls/spins as a result of airflow-induced engine stalls. As told by Grumman’s Chief Test Pilot Kurt Schroeder to Lou Drendel for his book Tomcat – Modern Military Aircraft series, “An engine stall creates two concerns: an immediate loss of thrust and potential damage to the engine. Damage to the engine results when the engine fuel control senses a deceleration in commanded compressor speed caused by the stall and tries to compensate for it by adding fuel. Without pilot action, the additional fuel combines with the disrupted airflow can quickly result in damaging turbine inlet temperatures. The loss of thrust produces a yawing moment which is normally easily countered by the aerodynamic stability for the aircraft. The airframe stability, however, varies as a function of airspeed and angle-of-attack and if a large thrust asymmetry exists (i.e. one engine in full afterburner with the other stalled) in an area that the aerodynamic stability is low, thrust will dominate. Without pilot corrective action, the aircraft could be driven into a departure from controlled flight and possibly into a spin.”

According to Schroeder, proper pilot corrective action would have been to reduce the thrust asymmetry and apply flight control inputs to counter the yawing moment. “While the aircraft retains very strong recovery control power, even in severe departures, prompt and correct application of the proper controls is difficult for the fleet pilot because of the disorienting nature of departures from controlled flight. Procedures which are easy to apply in a benign environment become much more than a challenge when suddenly subjected to the rapidly changing attitudes and accelerations of uncontrolled flight.”

As told by Shroeder these kinds of problems were resolved with the incorporation of the General Electric F110-GE-400 engines in the F-14B/D. “An example of the confidence we have in the recovery capability of the F-14 is a program we flew to evaluate the operability and asymmetrical thrust effects of the F110GE-400 engine. To accomplish the program objectives, intentional departures from controlled flight tests were required. While this type of work had been conducted during several programs with the TF30 powered aircraft, the test aircraft had always been equipped with a spin recovery parachute, deployable spin-recovery forward canards, special pilot escape provisions, and an emergency power system for hydraulic and electrical power. The immediate problem was that an F110 powered F-14 equipped with these provisions did not exist and to modify one would require unavailable time and money. The question was then raised: ‘Could we conduct the program with essentially an unmodified aircraft?’ After many discussions between Grumman and NAVAIR, the decision was made to proceed. Over 300 successful recoveries following the same number of intentional departures confirmed the confidence. […] The F110 has a tremendous stall margin everywhere […]. When you are maneuvering with the F110 engines, you can do whatever you want to do, whenever you want to do it.”

Photo by NASA

As Vickers started to push on the stick, he heard a loud pop, followed by a roar. He knew exactly what had happened and he transmitted, “Lion 52. Emergency, my RIO just ejected”

Here’s something you don’t see every day: the incredible photos in this post in fact show an F-14 Tomcat (actually the F-14D BuNo. 164341) flying without a canopy.

The U.S. Naval Aviator driving this Tomcat was then Lt. Geoff Vickers from Fighter Squadron 213 (VF-213) Black Lions and the story of how he was able to successfully land in this “unusual configuration” is quite interesting.

In 2002 Vickers and its squadron were detached to Naval Air Station (NAS) Fallon, Nevada, for strike training when he was tasked with giving the battle-group-air-warfare commander an orientation flight in the F-14D. As skipper of the cruiser in charge of the battle group’s air defenses he had the chance to experience several E-2C and EA-6B flights, and he remarked the fact that the Prowler guys hadn’t been able to make him sick.

As explained by Vickers himself to VFP62.com, his task for that flight was “to demonstrate the Tomcat’s performance and tactical capabilities. Though this flight was my first without a qualified radar-intercept officer (RIO) in the back seat, I had flown with a number of aviators who had very little Tomcat experience.”

The battle-group-air-warfare commander arrived at the squadron a half-hour before the brief to receive his cockpit-orientation lecture and ejection-seat checkout. Once in the ready room, Vickers and his wingman briefed the flight.

Vickers recalls: “I told the Captain that after the G-awareness maneuver, we would do a quick inverted check to verify cockpit security. Looking back, I should have recognized his anxiety when he mocked me and said, ‘Just a quick inverted check?’ then laughed. I didn’t realize hanging upside down with nothing but glass and 11,000 feet of air separating you from the desert floor might not be the most comfortable situation in the world for a surface-warfare officer.”

Vickers told the battle-group-air-warfare commander that during the flight they should have done an F-14D performance demo, followed by a couple of intercepts and by an air-to-air refueling from an S-3 Viking. “I was determined to avoid the temptation to intentionally make him sick and uncomfortable,” says Vickers.

After the take-off, Vickers checked the airspeed and since it confirmed he was above the 300 knots recommended to do the check, he rolled the aircraft inverted. “I decided not to really put on a lot of negative G and unloaded to about .3 to .5 negative G’s-just enough to make anything float that wasn’t stowed properly. If he was uncomfortable in such a benign maneuver, it would be better to find out then, rather than when we were racing toward the earth during a radar-missile defense.” As Vickers started to push on the stick, he heard a loud pop, followed by a roar. The cockpit filled with smoke, and they suddenly lost cabin pressure. “I first thought a catastrophic environmental-control system (ECS) had failed. I said to myself, ‘This is new. I’ve never even heard of something like this happening.’ Time compression turned the next few seconds into an eternity. I knew the first thing I had to do was to roll the jet upright and assess the situation. About three seconds after the first indication of a problem, I had the jet upright and knew exactly what had happened. I transmitted, ‘Lion 52. Emergency, my RIO just ejected.’ “

While Vickers was thinking he would have to make all the calls in the blind since he thought that all the noise of flying at 320 knots without the canopy would have never allowed the communications, he heard Desert Control contacting him: “Understand your wingman ejected?” “Negative, my RIO ejected. I’m still flying the plane.” “OK. Understand your RIO ejected. You’re flying the plane, and you’re OK?” Vickers replied he was ok but he didn’t tell he was flying a convertible F-14. “I was relieved to see a good parachute below me, and I passed this info to Desert Control. Very quickly after the emergency call, a F/A-18 pilot from the Naval Strike and Air-Warfare Center, who also was in the area, announced he would take over as the on-scene commander of the search-and-rescue (SAR) effort.” Vickers told his wingman to pass the location of the battle-group-air-warfare commander because “I could not change any of my displays. Once my wingman started to pass the location, I started dumping gas and put the needle on the nose back to NAS Fallon. One of our air-wing SH-60s was in the area and responded, along with the station’s UH-1N. The Captain was recovered almost immediately and transported to the local hospital for treatment and evaluation.”

After having raised his seat to have a better outside view during the landing, Vickers slowed the speed and decided to return to base “I did consider the controllability check, and I directed my wingman to check for damage to the vertical stabilizers-he found none. The faster I got on deck, the faster I would get warm. I slowed to approach speed in 10-knot increments at about 3,000 feet AGL (Above Ground Level) and had no problems handling the jet. As I approached the field, I was surprised at how quiet it got. The noise was only slightly louder than the normal ECS roar in the Tomcat. I’ll admit I felt silly saying the landing checklist over the ICS (the Intercom system, which allowed the F-14 pilot and RIO to communicate via the microphones built into their oxygen masks and headphone speakers in their helmets) when no one else was in the cockpit, but I didn’t want to risk breaking my standard habit patterns.”

The landing was uneventful, and Vickers was surprised to find how many people had come out to see the spectacle. “The magnitude of the situation finally set in when my skipper gave me a hug after I got out of the jet.”

Vickers and the battle-group-air-warfare commander were very lucky since all of the ejection and aviation-life-support-systems (ALSS) equipment functioned well: actually, the battle-group-air-warfare commander reported only two minor injuries to his face. But when Vickers talked to him he understood that even if he had briefed every single detail of the mission, he didn’t consider Captain’s fully perspective. “He said he didn’t know where to put his hands. Consequently, he just left them in loosely clenched fists on his lap, about two inches away from the ejection handle. It never occurred to me that someone would not know what to do with his hands. Obviously, I fly with the stick and throttle in my hands 95 percent of the flight, but I failed to consider his situation. The mishap board surmised that, during the inverted maneuver, he must have flinched when he slightly rose out of the seat and pulled the ejection handle. Now, before any brief, I try to place myself in the other person’s shoes (even if they are black shoes) and imagine what the flight will be like for him.”

Photo by Home of M.A.T.S. and U.S. Navy