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  • Chogy
    replied
    It had to be during a copper flag exercise back when copper flag was a much different exercise compared to today. Back then it was more EW-oriented, and nothing particularly exciting for any of the participants.

    We launched in a two-ship out of Eglin to support either Navy or Marine (I forget which) fighters protecting the Florida coastline near Panama City. They wanted us to simply present as some sort of intruder to the domestic ADIZ. No maneuvering. We thought "F this, this is boring."

    On the way out to the area to the South, one F-15 air aborted, leaving me and a back-seat rider in a D model as the sole entity. For whatever reason, we had a clean Eagle, no external fuel. External tanks are limited to mach 1.6. With the clean airplane, we had no limitations. We decided to present them with an almost impossible problem, a high & fast flyer. So at the Southern end of a slice of sky maybe 120 miles in size, we parked the throttles forward and left them there, and began a climb to 50,000' - can't go higher without a pressure suit.

    The mach began to wind up... 1.6, 1.7, 1.9 - and from our own scope, we saw the defenders muff the intercept badly. The simply didn't have the time, ooomph and fuel to reach us. The machmeter cracked 2.0 by the time we approached the coast. My backseater says "Uh, dude, you're booming the coast big time." Sure enough, we were already over land. Taking the throttles out of AB caused a violent forward G of maybe 1.5, hanging us in our straps straight forward. The deceleration was impressive.

    The single mach run had burned 75% of our fuel in just a few minutes, maybe 8 for the actual run. The remainder of the flight time was simply droning to and from the base. I forget, but probably 35 to 45 minutes.

    An average training sortie with one centerline tank was 1.5 to 1.6 hours total.

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  • Gun Boat
    replied
    A question for Chogy:

    Whats the fastest time you ever burnt through a tank of fuel in an F-15?

    Thanks.

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  • Mrit91
    replied
    Thanks for the information Chogy and Stitch.

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  • Stitch
    replied
    Yes, it is possible to "harden" electronic devices from an EMP burst, but it's fairly expensive, and usually makes the device much heavier than normal. It involves shielding the electronic components from the electromagnetic pulse using metal plates that absorb or block the pulse. One of the reasons military hardware tends to be more expensive than COTS hardware is that it is usually hardened against the effects of an EMP burst; if a COTS HDD costs $1,000, a military version would probably cost about $2,500.00.

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  • Chogy
    replied
    This is more of a physics question. Maybe someone will have an answer. I have no doubt that systems can be hardened; otherwise, a few measly stratospheric air bursts would take out an entire retaliatory missile force.

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  • Mrit91
    replied
    I have a doubt:
    Are there no protections against EMPs(Electro Magnetic Pulses)?
    Read that EMP can render electronic devices completely useless, in this way an enemy force can break through a formidable defense just by detonating a series of EMP devices!!!

    Leave a comment:


  • mako88sb
    replied
    Thanks for the replies Chogy and Ararat. Checked into it a bit more and found this site:

    Boeing 747SP Website - History for airframe# 22805

    Date of the incident was 2/19/1985 and repairs and inspections where completed by 4/25/1985. Bought by Global Peace Ambassadors in 2001. Operating Certificate suspended in 7/18/2005. Likely to be scrapped due to lack of maintenance.

    Leave a comment:


  • Ararat
    replied
    Originally posted by Chogy View Post
    To extrapolate - even without an incident, jets are regularly stripped to the bone for what are called "Heavy checks". My guess would be they did a complete heavy check and also used highly specialized devices to check for plastic deformation of the metal. No plastic (permanent) deformation, no cracks - good to go!

    Most traditional guys prefer metal airplanes to composite, because science truly understands metal's behaviors under load, whereas composites are still a bit new. Composites are very stiff. They tend to not bend, but simply explode into pieces when their ultimate load is passed. But sometimes hidden flaws like delamination or improper curing can create a ticking bomb in a component.

    But in the last couple of decades, huge strides in composites have been made, and I guess we have to trust the engineers that they are safe.
    Very true Chogy
    Also depending if it was(or not) sustained Gs beyond catagory and design limits of the aircraft, normally a special inspection procedures is in place with the use of none destructive technics (ultrasound, Xray, dye pent, etc) will be called out by eaither the structural repair manual or a special inspection procedure much like a hard landing inspection. Also like you said I would want to depanel the aircraft and give a a good visual like heavy check (C check at least), especially if its coming due in near future anyway.

    Also certain amount of damage can be acceptable if repairs are made or condition monitored (say crack growth on spar) by placing a special inspection program at certain intervals.

    All Aircraft are returned to service in an airworthy and safe for flight condition regardless of if its a passenger or cargo plane or whatever.

    Composite airfoils are much easier to inspect and they do not get skin buckling (like you might see on metal wings) from high G stresses. any hidden delamination can be seen by the use of xray.

    Leave a comment:


  • Chogy
    replied
    It would seem to me that considering what this plane went through, that they may of had to come up with new procedures to make absolutely certain it was safe to fly again.
    To extrapolate - even without an incident, jets are regularly stripped to the bone for what are called "Heavy checks". My guess would be they did a complete heavy check and also used highly specialized devices to check for plastic deformation of the metal. No plastic (permanent) deformation, no cracks - good to go!

    Most traditional guys prefer metal airplanes to composite, because science truly understands metal's behaviors under load, whereas composites are still a bit new. Composites are very stiff. They tend to not bend, but simply explode into pieces when their ultimate load is passed. But sometimes hidden flaws like delamination or improper curing can create a ticking bomb in a component.

    But in the last couple of decades, huge strides in composites have been made, and I guess we have to trust the engineers that they are safe.

    Leave a comment:


  • Chogy
    replied
    Transport aircraft are rated for a certain G load that is rarely approached in normal operations. But it is remarkably low, just 2 to 3 G. In an unusual attitude scenario, it is possible to load the airplane much higher, and the danger is bending and/or physically breaking spars and other structural members. Likewise, exceeding Vmax, red line, can also do damage. The jets that hit the WTC were well above red line... damn them for understanding kinetic energy is the square of the velocity. The cockpits were likely squawking like crazy with a thing called an overspeed clacker.

    Anyway, after an upset like this, they take the aircraft apart, inspect all of the load-bearing devices, especially the wing spars and the engine struts, magnaflux for cracks, and put everything under a microscope.

    These jets are well engineered and can often withstand loads much higher than their rated load. In this case, they found nothing wrong and put it back into service.

    I'd guess a 737 could pull 4 G and be fine. 6 G and it'd probably break up. Just estimating.

    We had a guy once save his life in an F-15 by pulling 12.5 G to avoid impact with the water, and the jet flew the next day. The same scenario in an F-16 would have resulted in a fatality, due to the G-limiting software. Needless to say, we preferred being in control over the G-available.

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  • mako88sb
    replied
    I have a question in regards to this Mayday episode I seen a couple years ago about China Airlines Flight 006:

    Panic Over The Pacific Part 1 - Air Crash Investigation/Mayday - YouTube

    Seems incredible that the stresses involved would actually rip the main gear doors off and do damage to the tail-plane yet somehow it was able to safely land. What an amazing plane! Near the end of part 5, they mention that it was put through "maneuvers and stresses that far outweighed it's known limits". It was repaired and put back into service. What I'm wondering is what kind of testing and airframe checks would they have to be done to be able to certify it for passenger use? It would seem to me that considering what this plane went through, that they may of had to come up with new procedures to make absolutely certain it was safe to fly again.

    Leave a comment:


  • Chogy
    replied
    The Coram quote leaped out at me when I read his book about Boyd. I'm not quite stooped yet, but I'm out of the game!

    The thing with the hands... it's SO real. Pilots do it unconsciously because a pair of hands is the quickest (maybe the only) way to get across two 3-dimensional flight paths to another person quickly and easily. At squadron parties with wives and such, it was inevitable, and the wives' eyes would roll back into their heads whenever it happened. In briefing rooms, we had two model airplanes on sticks, and they were used extensively to teach. They were invaluable.

    I wonder if squadrons even have their own bars any more. The official O'club people hated them because they took away business. We loved them. As soon as the last flight stepped, the bar was open, and we'd often debrief with a cold pitcher of beer.

    Leave a comment:


  • astralis
    replied
    chogy,

    There is no such thing as an ex-fighter pilot. Once a young man straps on a jet aircraft and climbs into the heavens to do battle, it sears his psyche forever. At some point he will hang up his flight suit - eventually they all do - and in the autumn of his years his eyes may dim and he may be stooped with age. But ask him about his life, and his eyes flash and his back straightens and his hands demonstrate aerial maneuvers and every conversation begins with "There I was at..." and he is young again. He remembers the days when he sky-danced through the heavens, when he could press a button and summon the lightning and invoke the thunder, the days when he was a prince of the earth and a lord of the heavens. He remembers his glory days and he is young again.

    Robert Coram, "Boyd"
    nice quote.

    we used to have a "Fighter Bar" prior to our move back to the Pentagon, and posted above the Bar was a sign that said:

    "ALL STORIES FROM OPERATIONAL LIFE ONLY. NO 'THERE I WAS, TYPING A STAFF SUMMARY SHEET...' "

    Leave a comment:


  • Chogy
    replied
    One other problem not anticipated by the engine folk was how often the engine would be "snatched" from one stop to the other at AOA and altitude extremes. This caused compressor stalling and other (worse) things. In the early 1970's, fuel controllers, that monitored throttle demands, were hydromechanical machines... like a WW2 carburetor + turbo-supercharging that could sense the basics of the world outside and the demands of the pilot, and schedule fuel.

    These worked OK. But like so much else, the advances in digital electronics paid huge dividends. Around maybe 1985, the DEEC (digital electronic engine control) was added to the F-100 engine, and the engine's behaviors were greatly improved. It allowed full throttle movement in all phases of flight. The DEEC also gave superior acceleration of the engine, and it was so pronounced that one could make excuses in the debrief... "Well I didn't have a DEEC airplane, which is why I lost the rolling scissors..." That sort of thing.

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  • Stitch
    replied
    Originally posted by Chogy View Post
    In a nutshell, you're at MAX for maybe 50% of the time, modulated within the A/B region for 25%, and at mil or below maybe 25%. There's no such thing as too much thrust. It is amazing how quickly and easily one could go from 25,000' and mach 1 to sea level and 200 knots.
    Chogy/Jimmy - I seem to remember there being problems with the F-100 engine in the F-15 early on because the pilots were cycling the engines a lot more in simulated combat than earlier engines, like the TF-30, due to the fact that the F-100 had a higher ST than earlier turbofans; it wasn't necessary to leave the throttle setting at mil power since there were times the pilot actually had to slow the aircraft to get a good firing solution. The designers of the F-100 hadn't planned for such high cycles, so the MTBF on the earlier engines was a lot lower than expected.

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