Still trying to replace the F14....

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Originally Posted By: Win
Originally Posted By: Astro14
.... She crashed the airplane because of poor flying skills.

She was too close abeam the carrier when she began the approach turn. To compensate, she skidded the airplane .... As the airplane rolled out on final, it was nearly 20 knots slow ....


Once the decision was made to push a bad position, only to wind up in an even worse one, was it still possible to avert the crash? Or do you get out then and there while you still have some control?


Win - Simply, you have to act early to maintain control of the airplane/situation. If you allow a situation to continue to degrade (like this one, or Air France 447) you can arrive at a place where the airplane is still in the air, but the crash is inevitable, where it cannot be saved or recovered.

If an engine fails on an airplane while it is slow, and configured for landing, you have to immediately increase power on the operating engine and, in many airplanes, reconfigure (adjust flaps, airspeed, etc.) immediately in order to maintain control.

IF an airplane slows below VMCA (Minimum control speed in the take-off configuration, a.k.a. air minimum control speed or minimum control speed in free air), you simply, by definition, cannot go to full power on the operating engine. While VMCA is defined at takeoff power (full thrust) it is ALSO defined at 5 degrees or less bank.

As the airplane increases in bank angle, the load factor, and hence, Angle of attack (AOA) increase, and a loss of control can happen at an even higher airspeed, because the AOA is also critical in controllability. In the F-14A, VMCA was 140 KIAS with one engine in full AB. VMCA was much slower for an engine at full dry (non AB, AKA military power) thrust. Closer to 120 KIAS.

Another critical bit: L/D max. In the drag curve, which looks like a big valley, there is a spot at which drag is the minimum. That spot is L/D max and it is the very floor of the valley.




Faster than that velocity (above L/D max) you are speed-stable, meaning that an increase in speed results in an increase in drag, which slows the airplane, while a reduction in speed reduces drag, which allows the airplane to accelerate. So, above L/D max, add power, and the airplane flies a bit faster. Minor changes in airspeed are dampened out by that speed stability.

It gets ugly below L/D max... because the curve rises (drag increases) as airspeed decreases. As you slow, the drag goes up, causing the airplane to slow even more. So, a slight power reduction, or a slight change in airspeed, suddenly requires a lot MORE power to keep the same speed. The farther to the left of the curve, the worse it gets.

Note that the L/D max numbers and curve change with a change in aircraft configuration (flap setting, gear, etc.), but the basic principle is true whether you're flying flaps up, or full flaps for landing, or something in between.

So, you slow the airplane below L/D max, then it takes a LOT of POWER to fly at that speed. If you've simultaneously slowed below VMCA, you're in deep trouble. You don't have the flight control authority to handle the thrust asymmetry, but you NEED that extra thrust to stay in the air.

Commercial airliners fly well above L/D max when on approach, so they are speed stable.

Navy fighters are different. There are structural limitations on a Navy landing, including arresting gear engagement speed (which puts load on the tailhook and airframe). For example, 119 Knots was the max gear engagement speed for an F-14 at 54,000# landing weight. So, they generally fly pretty close to L/D max when on approach, to minimize the landing speed.

Which means that you can't get slow on approach, or it's hard to get out of the L/D max drag situation.

As an example, in the F/A-18, if you lost an engine when fully configured, you had to move the flaps to 1/2 immediately. The airplane could not maintain altitude on one engine with gear down and full flaps. There was simply too much drag (a point I learned in the simulator - it simply wouldn't fly, not even in max AB on the one good engine...) from the fully extended flaps and drooped ailerons.

So, let's take a 767 for example - lose an engine on final, normal configuration (flaps 30) and you've got three choices: 1. add power on the good engine and land. 2. add power, retract the flaps to 20 degrees, increase the approach speed and land. 3. Go to full power, retract the flaps to 20, and raise the gear as you climb out. Simple, docile airplane. Lots of options. But all must be done immediately.

In the F-14 you must:

1. add power immediately. You cannot allow the airplane to get slow.
2. retract speed brakes (because of the steep approach angle, Navy fighters landed with speed brakes extended to increase drag, which allowed a higher engine power setting and thus, better engine response)
3. disengage DLC (direct lift control, which extended spoilers on the wing to allow for glideslope adjustment without using engine power since the TF-30 engine had poor response)
4. adjust AOA from 15 to 14 (15 is normal, but a lower AOA increases controllability).

It all had to be done quickly. Very quickly. Even experienced guys would likely take the airplane around (initiate a full-power wave-off) to sort through the reconfiguration, changes, and re-trim everything (I didn't even talk about trim in all this, but trim all changes with power and airspeed, and with an engine failure, rudder trim in particular has to be significantly adjusted, either through normal trim, or a heavy foot on the rudder on the operating engine side).

Very few pilots would re-configure the airplane while in the approach turn, adjusting speed, trim, configuration and AOA while maintaining the precision turn... As apoint of reference, your goal was to cross the ship's wake at 375' in a 27 degree angle of bank and roll wings level to arrive on final at 350'. If you were ten feet high or low, and more than one know fast or slow, the LSO (see more below on LSOs) would be able to see that and judge your corrections. The LSO is watching from the time an airplane arrives abeam the ship and begins the turn.

And even if you were able to manage all that with precision, a single engine landing requires a couple of arresting gear considerations/calculations, so you might not be able to land on that approach anyway.

In the case of Kara Hultgreen, no engine power adjustment was made after the engine compressor stall/failure. The airplane was rolled into a 27-28 degree angle of bank for the approach turn (which increased load factor and AOA, and increased the drag). As the airspeed bled off, the airplane was climbing the drag curve below L/D max and as it got slower, the drag rose, more and more.

When she rolled out on final, the LSO (A Landing Signal Officer (LSO) is a Naval Aviator specially trained to facilitate the "safe and expeditious recovery" of naval aircraft aboard aircraft carriers - I was an LSO, if that wasn't obvious) waved her off (told her to go around) because he could see how slow the airplane was - it was way outside of normal parameters...

But she was on the back side of L/D max...and full dry thrust on the good (right) engine didn't arrest the descent - because the drag was so high... The LSO called for "raise your gear" in an attempt to reduce the airplane drag. Some LSOs have said that he shouldn't have made that call because he was "flying her airplane" but I think it was a great call - it was clear that the LSO was the only one who WAS flying that airplane.

When the LSO called for "burner" - she selected it. But where was the that airplane? Below VMCA. Well below it. And well below L/D max. At that point, it could not have been saved if Chuck Yeager himself had been teleported into that cockpit. There was so much drag, and at such low altitude, there was just no time to reduce AOA enough, to reduce drag enough, to regain control and add the energy needed to avoid a crash.

The failure to maintain flying speed was a listed causal factor. She needed to add power when the left engine quit. She didn't.

What will forever be speculation: did she know that the engine failed? She should have. The airplane was getting slow. The engine instruments would've shown the loss of RPM and fuel flow. The compressor stall warning was on. It was all there...all the information.

But there was absolutely no action taken in response: no increase in engine power on the good engine. DLC remained engaged. Speed brakes remained extended. (note that both DLC and speedbrakes are retracted when either throttle hits the military power detent - the engineers ensured that the drag would be reduced for a go-around/wave-off and they both did when she went to full power on the right engine).

As I've said before in this thread and my F-14 thread, the Tomcat wasn't easy to bring aboard. I've explained the simple aerodynamics, but the F-14 was even more complex - with slotted flaps and slats, DLC, spoilers and stabilators for roll control, and the poor engine response of the TF-30s at approach power settings. The discussion above doesn't get into the nuances and complexities of an F-14 landing.

It's my belief that she was nearly overwhelmed by the airplane when it was operating normally, as evidenced by her training records and performance. She didn't get the airplane to the right position abeam the carrier - the very simple job of putting the airplane in the right place. When things started to go wrong, she was unable to respond. It was too much for her. She failed to respond to the engine failure (that she induced through skidding the airplane, again, a horrible technique) because she became task-saturated and unable to understand what was happening.

The system that allowed her to be in that airplane, the airplane that was too much for her skills and ability, was what ultimately killed her. The real failure in all of this was a failure in leadership.

https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/2911273/1

https://en.wikipedia.org/wiki/Landing_Signal_Officer
 
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Wow, thank you for that thorough and lucid response to the question.

I was going to go out to lunch, but I made a sandwich and sat back down at the desk to absorb that.

Quote:
.... The real failure in all of this was a failure in leadership.


Yes.
 
Originally Posted By: Win
Wow, thank you for that thorough and lucid response to the question.

I was going to go out to lunch, but I made a sandwich and sat back down at the desk to absorb that.

Quote:
.... The real failure in all of this was a failure in leadership.


Yes.


You're welcome. I saw your question yesterday, but was at work, and knew I needed time to give a complete answer.

Cheers,
Astro
 
Difficult to bring on board? It's difficult to read how to bring it on board.
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Extremely good, and most appreciated input, Astro.

First I ever read about that incident. It seems underestimating the plane was the mistake of more people than herself.

Also highlights how arbitrary the aftermath of these disasters are. .3 seconds live, .3 seconds die.
 
Originally Posted By: Astro14
The Navy saddled the F/A-18 E/F with ENORMOUS drop tanks of 500 gallons (instead of 330 gallons, like the A/B/C/D Hornet) that caused huge drag, and resulted in terrible top speed, just to demonstrate having "long range" but...it's really not...
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Originally Posted By: Astro14
.....The Achilles Heel of the Super Hornet is the angle of the weapon pylons. To reduce flutter at transonic speeds, they were angled out by 4 degrees. They're NEVER directly in the airflow and ALWAYS create high drag.
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Originally Posted By: Astro14
...I've supercruised a slick F-14B (supersonic without AB), so adding 30% more thrust with the -429 engine would easily get a QS or T21 to supercruise (while the Hornet struggles to get through Mach 1 even in full AB when it's carrying weapons).
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Sierra-Oscar-Alpha-Bravo......

Wow....just wow....
 
Originally Posted By: Astro14
She was too close abeam the carrier when she began the approach turn. To compensate, she skidded the airplane, using left rudder, a horrible technique that caused an engine stall. She failed to recognize the engine stall, she failed to keep the airplane at the proper speed, she failed to identify the stall to her RIO (good guy named Matt Klemish, one of my students in VF-101), and she continued the approach without reconfiguring the airplane for a single engine approach (speed brakes in, DLC off, 14 units AOA).
Wow...she was Tango Uniform as soon as she was too close abeam. Add a skidded turn + a compressor stall + an avalanche of errors...

It's a shame it cost her her life. Good her RIO survived.

Batsy-Patsy...what a form of things to come.....
 
I was in Desert Storm with VAW-116 aboard the USS Ranger CV-61, we had VF-1 and VF-2 in the CAG with their Tomcats, shame they did away with them so soon, as previously mentioned by Astro 14 the ST21 and Quickstrike F14D would have been a very lethal combo.
http://www.anft.net/f-14/f14-history-f14x.htm
 
That's a bunch of misrepresentation, Bill. An amateur attempt at recreating the mishap on MS FS2004.

I went through the crash in detail earlier, but here's what's wrong with the video:

1. The airplane wasn't on a straight in approach, it was turning. Standard day pattern (Case 1 recovery)
2. The engine didn't just quit, it stalled because she applied left rudder to skid the turn and disrupted airflow into the left intake.
3. She didn't go full left rudder and full power, she used left rudder, which stalled the engine, then she failed to increase power, allowing the airplane to decelerate over the entire turn (roughly 30 seconds) and THEN she approached centerline.
4. She didn't really overshoot, she was flying in a skid.
5. The airplane crashed despite right rudder for the aerodynamic reasons I outlined earlier. The video says she applied left rudder.

It was the Gulf of Sidra airplane. They got that right. The rest is specious oversimplification with pretty simulator screenshots that had nothing to do with the actual flight parameters.

The grainy crash footage at the end was real.

All too real...you can see the flash of the seat rocket motors firing.

Klem made. She didn't.
 
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Thanks Astro. I found this video while I was just surfing You Tube watching various airplane videos. I didn't buy into the engine just "quitting" after reading your detailed post on the accident. A lot of these guy post this stuff, knowing just enough to be dangerous. The real crash footage didn't last but a couple of seconds. And you couldn't determine much if anything from it.
 
Astro,

One thing I've always wondered about with modern jet engines like those in the F-14. Is if they can be compressor stalled by a slight interruption in air flow into the intake, (like in the Hultgreen accident), how can these newer fighters like the latest Mig's and F-22's with vectored thrust, make these abrupt maneuvers and not experience the same stalling condition?

For example, when you watch these Soviet pilots do these "Cobra Maneuvers" at airshows, where they rotate the aircraft well beyond 90 degrees while in forward flight, and practically start ramming air into the tailpipe, one would think it would produce a guaranteed compressor stall for sure. But they seem to handle it fine.

I thought I remember reading back in the 60's, (correct me if I'm wrong), when the small business jets like the Lear 24 and such, were coming of age, that it was a cardinal rule to never try to start the engines with a wind blowing into the tailpipes. It was recommended the aircraft be towed into the wind before the engine starting procedure was attempted.

Is it that jet engine technology has advanced that far? Or is it a different type of engine all together in regards to the compressor section?
 
Jet engine control technology has seen incredible improvements since the early 1960s, when the TF-30 engine was designed. To be fair, there have been improvements in metallurgy, engine design, and other areas but going from hydro-mechanical engine controls to electronic engine controls was a huge step forward.

The F-14 airframe was incredibly advanced when it was built. I'll argue that nothing since can meet the requirements that it did, but at the time, it was a response to the failure of the Macnamara-imposed F-111 airframe as a fighter for the Navy. So, to bring the F-14 design into production quickly, several carry-overs from the F-111 were made.

Including the TF-30 engine that was designed in the early 1960s (first flight was 1964, I think). The TF-30 was ground-breaking when built. An afterburning twin-spool turbofan. It cut thrust-specific fuel consumption in half over older turbojet designs, and performed quite well in the F-111. In the F-111, the TF-30 engine was reliable, performed well, and was even up-rated in power over its service life.

But fighter pilots are notoriously hard on engines. And the F-14 pilots were hard on the TF-30. It wasn't initially intended for high AOA, throttle slams, gun gas ingestion, high yaw rates, and other airflow disruptions from air combat maneuvering. The TF-30 got a system called mid-compression bypass (MCB) - 7th stage bleed air was dumped overboard during (yep, you guessed it), high AOA, high yaw, gun firing, and during landing gear down or refueling probe extension. Dumping that compressor air overboard cut compression ratio (and also thrust) considerably, but it kept the engine running during demanding conditions.

The Navy never intended to power the F-14 with the TF-30 past the first dozen prototypes. It was a carry-over from the F-111 to get the airplane into production. In 1973 the Navy flew the "Super Tomcat" with the DFE prototype engine (which added nearly 10,000# of thrust per engine and added electronic engine management).

But as the Vietnam War was winding down, and inflation was rampant, Congress was slashing the budget, and Congress told the Navy* that they couldn't pay for a new engine for their airplane because it was good enough as is. It was flying. Congress pulled the funding on DFE and pulled the funding from Grumman on integrating a new engine.

It's not really fair to call the TF-30 a "modern" engine when it was designed in the late 1950s with hydromechanical controls. Ground-breaking, yes. Huge increase in fuel performance. But not really modern.

The truly modern engines, like the ones to which you refer, are wonderful. Powerful, reliable, controlled by FADEC's and with variable stator vanes and other tricks to compensate for airflow disturbances. The TF-30 was from a different phase in the evolution of jet powerplants.

Back to the F-14...

The MCB valve on Hultgreen's airplane was found closed in the wreckage, and it should've been open with gear down. Many have pointed at the TF-30 engine, with its history of in flight failures, compressor stalls and reliability problems in the F-14 and attributed the crash to the engine. That's not really the whole story. The engine shouldn't have stalled...but that doesn't explain her failure to fly the airplane. Engine quits in the F-14 - you fly the jet. Period. No excuses just because you're the first female to fly the jet. Are you a pilot or not?

I've had dozens of compressor stalls in the F-14. I was hard on engines, at times. Flew and restarted every one of them. That's what a real pilot does. I honestly can't remember every one of them ... they happened. That's it.

She induced an engine failure by skidding the airplane. She had to skid the airplane because she didn't fly it to the proper place abeam the ship for a Case 1 visual pattern. The essence of being a pilot: put the airplane where it's supposed to be. She was too close to the ship and had to correct for that, and she chose, on many occasions, to skid the plane. Horrible technique in that airplane with that engine. NOBODY I knew would skid the airplane to fix that. The flight manual cautioned against skids because of the possibility of an engine stall.

So, she chose a technique that the flight manual told pilots NOT TO DO. What should you do? Find yourself too close abeam, delay the turn a bit, wrap up the turn at a higher angle of bank or a bit, and you've fixed your problem. Any good Navy pilot knew that...put the airplane where it needs to go. Skidding works in Cessnas...not in fighters.

When faced with an engine failure, she allowed the jet to become slow. She failed to fly the airplane. Failed to add power to maintain proper approach speed (and controllability). Failed to recognize the stall/failure. Failed to re-configure for a single-engine approach.

The TF-30 engine in this airplane was a weak link. We all knew that.

But the crash was caused by a weak pilot.


*Congress micro-manages the military budget down to the dollar. You get funded for things by line item and it's very specific. You can buy X number of these items at this cost. With airplanes, it includes what radio, or what engine, right down to the tiny details. In buying a ship, we get ships delivered with old design specifications or parts (e.g. chalkboards in the pilot ready rooms) because Congress was that specific in the original contract and it's easier/cheaper to replace those outdated parts (e.g. Whiteboards in the pilot ready rooms) than it is to change the Congressionally-imposed set of specifications.

In the case of the F-14, even though newer engines became available in the 1970s, Congress insisted on the TF-30 to keep a cap on F-14 costs. When John Lehman became SECNAV in 1980 - he started pushing for a new engine. The Navy had lost several F-14s to stall/spin accidents due to engine failures. The cost of new engines would've been a lot less than the replacement cost of those airplanes. In 1986, he got approval to buy the GE F-110 engine for the F-14 and the F-14A+ (as it was originally known) was first delivered in 1988. No more compressor stalls. Far better performance/thrust. Better time to climb and mission performance. The GE F-110 put out the power that the F-14 was intended to have from day one, when it was designed.

Ironically, the F-110 engine was a USAF development as the F100 PW-100 engine that was originally in the F-15 and F-16 was having, you guessed it, compressor stalls and other reliability issues. It required development to fix (later versions like the F100 PW-220 were far superior) and the USAF got GE to compete in the fighter engine program to have an alternative in case the fixes to the F100 weren't successful.

The DFE in the early Tomcats was a parallel program to the F100 being sourced by the USAF. In the 1960s, the plan was for the USAF to buy the F100 for their F-15s and the USN to buy them for their F-14s. Again, Congress intervened and killed the USN $$.

The "Super Tomcat" in 1973, with new engines.

 
Originally Posted By: Astro14
Quite clearly. All too clearly.



I was involved, tangentially, in the mishap investigation. I was, at airplanes, but allowing her to fly the Tomcat was a mistake that ultimately took her life.



I always kept that in mind when I was training, and judging the performance of, my students in the carrier landing phase. Not every one of my students passed. But every one that did pass, and flew Tomcats in the fleet, is still alive.


Man that's cold.

The more I converse with you the more I understand I could never have cut it in the military.

Not a slam on you.
 
Originally Posted By: turtlevette
Originally Posted By: Astro14
Quite clearly. All too clearly.
I was involved, tangentially, in the mishap investigation. I was, at airplanes, but allowing her to fly the Tomcat was a mistake that ultimately took her life.

I always kept that in mind when I was training, and judging the performance of, my students in the carrier landing phase. Not every one of my students passed. But every one that did pass, and flew Tomcats in the fleet, is still alive.


Man that's cold.
The more I converse with you the more I understand I could never have cut it in the military.
Not a slam on you.


No offense but I don't know why you feel it is cold. The purpose of training is not to kill the students, it is to provide pilots to defend this nation. Astro served that function. In doing so he did not allow candidates who were unsuited to the mission go forward into a situation where they were likely to kill themseves and others who would be relying on his/her skill. I call that an act of compassion. I think you could indeed make those decisions if you were given the responsibility to do so. Too many people, too many families would be counting on you to make them. Thank God there are still some people who take responsibility.
 
Originally Posted By: turtlevette
Man that's cold. The more I converse with you the more I understand I could never have cut it in the military. Not a slam on you.


A person either possesses the talent and skill to operate a $30-$40 million jet off a carrier, or they don't. If they don't there is no way to sugar coat that fact. Or worse, B.S. their abilities into thinking they do, and pushing them forward under false pretenses. That's what politics pushed the military to do with Hultgreen. You see what it ended up accomplishing.
 
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