Interesting F-14 side topic ... the growing pains of development of every new fighter aircraft.
https://www.youtube.com/watch?v=Jq52ASESk9o
https://www.youtube.com/watch?v=Jq52ASESk9o
Still trying to replace the F14....
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Originally Posted By: ZeeOSix
Interesting F-14 side topic ... the growing pains of development of every new fighter aircraft.
https://www.youtube.com/watch?v=Jq52ASESk9o
I really loathe these amateurish recreations on YouTube. I mean, it's sophisticated flight sim stuff, but many aircraft details are wrong (the cockpit displays are reversed, with the attitude display BELOW the heading display, the engine nozzle position on the ground and in flight is wrong, the gratuitous AB shot mid-flight, which didn't happen, the standby gyro is wrong, and used for showing the "gentle pitching").
The cause of the crash was well-documented at the time (1970) and the voice-over on this is inaccurate...
A cracked line caused the loss of hydraulic system pressure in the combined system, which powered landing gear, flaps, hook, brakes, refueling probe and nosewheel steering in addition to the left side inlet, left wingsweep motor, and rudders and horizontal stabilizers. As the airplane was being flown back, the flight hydraulic system failed, too. It powered the right side inlet, right wingsweep motor, and rudders and horizontal stabilizers.
The video implies that this caused the gentle pitching.
It didn't.
With zero hydraulic pressure of any kind, it simply can't be flown. But Grumman wasn't stupid, there was a third system, a Back-Up Flight Control Module. (BFCM). The BFCM was a electric hydraulic pump that used trapped hydraulic fluid to power only the rudders and horizontal stabilizers. It had two modes: low, for inflight use, and high, for landing. Use of high was limited due to overheating concerns.
Landing gear extension was by nitrogen bottle. Flap extension used the spoiler module. Hook was manually released but couldn't be retracted.
The airplane was flyable in the landing configuration if the BFCM was switched to high mode. Low mode was automatic, high mode had to be selected. As they were coming back and had the second hydraulic failure, the BFCM came on (automatically, as designed).
The crew thought that the BFCM would automatically go to high mode with gear down (to be fair, this was under consideration during the design phase, but in the actual prototype as well as the production airplane, high had to be manually selected).
It didn't. So, there wasn't enough hydraulic power to control the airplane in the landing configuration. Extensive testing (done later) of the BFCM demonstrated sufficient controllability for landing while in mode, but not while in low mode.
The gentle pitching was PIO - the airplane wasn't responding, so the pilot was making larger inputs that coupled with the airplane's response rate to cause increasingly large pitch excursions.
The crash could've been prevented if the crew had selected high mode on the BFCM. Right hand pilot console, towards the back, lift the guard to engage (yes, I still know where that little switch was).
The Tomcat went back to stainless steel lines and accumulators, adding weight, but solving the line fatigue issue.
To say that the airplane never had hydraulic issues as a result is, well, a joke. It had lots of them...that's part of why it was retired. The maintenance on an airframe that was this complex was high...and it was a very complex airplane from a hydraulic perspective...
But yes, to your point, all new airplanes have teething issues. The F-14 had many. Titanium hydraulic lines was certainly one of them.
Leaving the Back-up flight Control module in low mode caused this crash, however. The video leaves that critical point out...
Interesting F-14 side topic ... the growing pains of development of every new fighter aircraft.
https://www.youtube.com/watch?v=Jq52ASESk9o
I really loathe these amateurish recreations on YouTube. I mean, it's sophisticated flight sim stuff, but many aircraft details are wrong (the cockpit displays are reversed, with the attitude display BELOW the heading display, the engine nozzle position on the ground and in flight is wrong, the gratuitous AB shot mid-flight, which didn't happen, the standby gyro is wrong, and used for showing the "gentle pitching").
The cause of the crash was well-documented at the time (1970) and the voice-over on this is inaccurate...
A cracked line caused the loss of hydraulic system pressure in the combined system, which powered landing gear, flaps, hook, brakes, refueling probe and nosewheel steering in addition to the left side inlet, left wingsweep motor, and rudders and horizontal stabilizers. As the airplane was being flown back, the flight hydraulic system failed, too. It powered the right side inlet, right wingsweep motor, and rudders and horizontal stabilizers.
The video implies that this caused the gentle pitching.
It didn't.
With zero hydraulic pressure of any kind, it simply can't be flown. But Grumman wasn't stupid, there was a third system, a Back-Up Flight Control Module. (BFCM). The BFCM was a electric hydraulic pump that used trapped hydraulic fluid to power only the rudders and horizontal stabilizers. It had two modes: low, for inflight use, and high, for landing. Use of high was limited due to overheating concerns.
Landing gear extension was by nitrogen bottle. Flap extension used the spoiler module. Hook was manually released but couldn't be retracted.
The airplane was flyable in the landing configuration if the BFCM was switched to high mode. Low mode was automatic, high mode had to be selected. As they were coming back and had the second hydraulic failure, the BFCM came on (automatically, as designed).
The crew thought that the BFCM would automatically go to high mode with gear down (to be fair, this was under consideration during the design phase, but in the actual prototype as well as the production airplane, high had to be manually selected).
It didn't. So, there wasn't enough hydraulic power to control the airplane in the landing configuration. Extensive testing (done later) of the BFCM demonstrated sufficient controllability for landing while in mode, but not while in low mode.
The gentle pitching was PIO - the airplane wasn't responding, so the pilot was making larger inputs that coupled with the airplane's response rate to cause increasingly large pitch excursions.
The crash could've been prevented if the crew had selected high mode on the BFCM. Right hand pilot console, towards the back, lift the guard to engage (yes, I still know where that little switch was).
The Tomcat went back to stainless steel lines and accumulators, adding weight, but solving the line fatigue issue.
To say that the airplane never had hydraulic issues as a result is, well, a joke. It had lots of them...that's part of why it was retired. The maintenance on an airframe that was this complex was high...and it was a very complex airplane from a hydraulic perspective...
But yes, to your point, all new airplanes have teething issues. The F-14 had many. Titanium hydraulic lines was certainly one of them.
Leaving the Back-up flight Control module in low mode caused this crash, however. The video leaves that critical point out...
Originally Posted By: Astro14
The airplane was flyable in the landing configuration if the BFCM was switched to high mode. Low mode was automatic, high mode had to be selected. As they were coming back and had the second hydraulic failure, the BFCM came on (automatically, as designed).
The crew thought that the BFCM would automatically go to high mode with gear down (to be fair, this was under consideration during the design phase, but in the actual prototype as well as the production airplane, high had to be manually selected).
It didn't. So, there wasn't enough hydraulic power to control the airplane in the landing configuration. Extensive testing (done later) of the BFCM demonstrated sufficient controllability for landing while in mode, but not while in low mode.
Sometimes design lessons are learned the hard way. Also, the importance of proper pilot training (especially in emergency situations) can't be over emphasized. As with any accident, there are more than one factor stacking up at the same time.
The airplane was flyable in the landing configuration if the BFCM was switched to high mode. Low mode was automatic, high mode had to be selected. As they were coming back and had the second hydraulic failure, the BFCM came on (automatically, as designed).
The crew thought that the BFCM would automatically go to high mode with gear down (to be fair, this was under consideration during the design phase, but in the actual prototype as well as the production airplane, high had to be manually selected).
It didn't. So, there wasn't enough hydraulic power to control the airplane in the landing configuration. Extensive testing (done later) of the BFCM demonstrated sufficient controllability for landing while in mode, but not while in low mode.
Sometimes design lessons are learned the hard way. Also, the importance of proper pilot training (especially in emergency situations) can't be over emphasized. As with any accident, there are more than one factor stacking up at the same time.
I read that another nail in the F-14's coffin was the cost of the Phoenix missiles they used. At the time the radar in them was so powerful, it had to be cooled with liquid nitrogen, which was expensive to keep onboard the ships. I don't know how true this is or how modern electronics could do away with that system.
Originally Posted by Brigadier
I read that another nail in the F-14's coffin was the cost of the Phoenix missiles they used. At the time the radar in them was so powerful, it had to be cooled with liquid nitrogen, which was expensive to keep onboard the ships. I don't know how true this is or how modern electronics could do away with that system.
So much information on the internet...
And so much of it is completely wrong...
Yes, the AIM-54A needed to be cooled. It's radar was powerful (more powerful than the radar first fitted to the F-16, by the way) and the electronics needed to be cooled. So did the AWG-9 radar in the F-14 and liquid cooling (liquid, not liquid nitrogen) was the only way to get the heat out of the system*. The AIM-54C that came out in 1986 (with improved electronics and transmitter) did not need to be cooled.
Both the AWG-9 and AIM-54 used liquid coolant that was cooled by the airplane's ECS. The coolant pump for the AIM-54A was contained in the weapon rail.
Liquid nitrogen was made aboard the ship for the AIM-9 Sidewinder, which WAS cooled by liquid nitrogen*. Liquid oxygen was also made aboard ship, for the aviators.
So, yes, ships made liquid nitrogen, for a different missile.
Taking the Phoenix (AIM-54) off the ship saved costs and inventory, but saved nothing in liquid nitrogen.
By the time the AIM-54 was taken off the ships, they were all AIM-54C variants anyway, which didn't need the internal liquid cooling either.
*The AWG-9 radar was built around a powerful transmitter. Really powerful. Like, an order of magnitude higher than other US fighters. It was built to "burn through" jamming systems on Soviet bombers. That created enough heat that it had to be liquid cooling - air cooling wasn't enough...
**The infrared seeker had to be made very cold to work well. Liquid N2 was used through the later versions of the AIM-9, including the AIM-9M. My understanding is that the AIM-9X uses an internal cooling system.
I read that another nail in the F-14's coffin was the cost of the Phoenix missiles they used. At the time the radar in them was so powerful, it had to be cooled with liquid nitrogen, which was expensive to keep onboard the ships. I don't know how true this is or how modern electronics could do away with that system.
So much information on the internet...
And so much of it is completely wrong...
Yes, the AIM-54A needed to be cooled. It's radar was powerful (more powerful than the radar first fitted to the F-16, by the way) and the electronics needed to be cooled. So did the AWG-9 radar in the F-14 and liquid cooling (liquid, not liquid nitrogen) was the only way to get the heat out of the system*. The AIM-54C that came out in 1986 (with improved electronics and transmitter) did not need to be cooled.
Both the AWG-9 and AIM-54 used liquid coolant that was cooled by the airplane's ECS. The coolant pump for the AIM-54A was contained in the weapon rail.
Liquid nitrogen was made aboard the ship for the AIM-9 Sidewinder, which WAS cooled by liquid nitrogen*. Liquid oxygen was also made aboard ship, for the aviators.
So, yes, ships made liquid nitrogen, for a different missile.
Taking the Phoenix (AIM-54) off the ship saved costs and inventory, but saved nothing in liquid nitrogen.
By the time the AIM-54 was taken off the ships, they were all AIM-54C variants anyway, which didn't need the internal liquid cooling either.
*The AWG-9 radar was built around a powerful transmitter. Really powerful. Like, an order of magnitude higher than other US fighters. It was built to "burn through" jamming systems on Soviet bombers. That created enough heat that it had to be liquid cooling - air cooling wasn't enough...
**The infrared seeker had to be made very cold to work well. Liquid N2 was used through the later versions of the AIM-9, including the AIM-9M. My understanding is that the AIM-9X uses an internal cooling system.
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Interesting that someone wrote an article about the gap not filled since the f-14 was retired. Kind of said that the need for that range and speed aircraft is coming back.
https://www.yahoo.com/news/why-navy-misses-old-f-135300750.html
https://www.yahoo.com/news/why-navy-misses-old-f-135300750.html
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