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If the EPU (Emergency Power Unit) and batteries plus engines fail on a modern fighter aircraft, basically they will fall out of the sky, there is no dead stick landing - is this correct?

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    $\begingroup$ There may also be a RAT on board $\endgroup$ – ratchet freak Oct 26 '14 at 10:28
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    $\begingroup$ I don't think anyone really expects fighter to do a dead-stick landing under any conditions. In many mission profiles the aircraft is too low to glide anywhere useful anyway. $\endgroup$ – Jan Hudec Oct 26 '14 at 21:48
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    $\begingroup$ Are you asking if there are other power sources that could help with a dead-stick landing, or whether an aircraft is controllable without any electrical/hydraulic power? $\endgroup$ – GdD Oct 27 '14 at 8:17
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    $\begingroup$ @JanHudec tell that to the high altitude interceptor pilots... Not everyone is down in the dirt playing the penetration bomber game. $\endgroup$ – jwenting Oct 27 '14 at 12:24
  • $\begingroup$ @jwenting: They are ever since high-altitude SAMs rendered flying above the enemy's air defences obsolete as a strategy for avoiding getting shot down, way back in the sixties. $\endgroup$ – Sean Jul 29 '18 at 0:06
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How Are Modern Fighter Aircraft Controlled?

The F16 was the first US military aircraft to be designed around the revolutionary fly-by-wire concept. This meant there were no direct mechanical linkages between the cockpit and major control surfaces, and that all pilot input was electronically carried to the hydraulic system via wire. However, since the F16 burst into the scene, there have been further major advancements in aircraft systems design. Late Gen 4 aircraft, such as the F/A 18 Super Hornet, are designed around a concept now called control-by-wire. Control-by-wire aircraft not only have removed mechanical linkages to the hydraulic system, but now the pilot is only a voting member. This means that all input is received by a computer bank that then computes what it thinks the pilot is intending to do, and then autonomously operates the control surfaces to achieve the effect. This means that Gen 4 aircraft rely heavily on both computer integrity (and there are plenty of self-healing backups), and the power required to run those systems.

Power Failure

If there was a catastrophic total electrical failure and the only remaining power supply was the battery, the only option is for the pilot to restart a generator. In the event that the engines were operating and all power generation was destroyed, the aircraft would only be flyable for the duration which the battery could provide power to the aircraft--that's a very limited duration.

Possible other scenarios could include a dual-engine failure. In this instance, the aircraft may be able to fly fast enough to generate enough airflow down the turbine to turn the generator and perform an airstart, but this would only be useful in a dual engine failure, and only if there was enough altitude and airspeed to trade to make it a realistic option. Otherwise, the battery would probably be used to power the APU, and attempt a relight. Again, if both engines relit and the generators (including the APU) failed to produce power, then the aircraft would not be flyable.

But what about the RAT?

Although currently in limited use on some trainer aircraft like the T-45, modern fighter aircraft do not use a RAT.

So what usually happens in a total electrical failure?

If the aircrew cannot get a generator back online then they eject.

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    $\begingroup$ Wikipedia is often wrong, and this is one of those instances. Modern US fighter aircraft do not use RATs. Even older aircraft like the F-16 elected to use an EPU vice RAT. Neither the Super Hornet, nor other late Gen 4/Gen 5 aircraft use them. $\endgroup$ – Rhino Driver Nov 15 '14 at 3:07
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    $\begingroup$ Its also worth noting that modern electrical systems are so reliable you're probably more likely to inadvertently kill both engines and eject than you are to totally lose all power because of a system failure. $\endgroup$ – Rhino Driver Nov 15 '14 at 4:00
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    $\begingroup$ @ChrisW The Growler has RATs to power its pods, but the Super itself, E/F/G models, relies on windmilling the engine to provide backup HYD when the engine dies. I'm not sure about the legacy models. $\endgroup$ – Rhino Driver Nov 15 '14 at 19:45
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    $\begingroup$ @DavidRicherby I fly the Rhino. $\endgroup$ – Rhino Driver Nov 15 '14 at 19:51
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    $\begingroup$ @raptortech97 Once the computers turn off its a crap shoot. Best case, you become a glider in the direction you were flying. Worst case, the computers died when the controls surfaces were weird and you instantly depart. In the rhino, the batteries only give 5-10min of flight time (dependent on aircraft configuration and systems powered that drain the battery) if everything else is dead. $\endgroup$ – Rhino Driver Apr 27 '15 at 19:16
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Define "modern". The A-10 is only 38 years old, is still in service and is expected to remain so until at least 2020 (its planned replacement, along with many other current service aircraft including the F-15E, F-16 and F/A-18, is the much-maligned F-35 program). It has redundant hydraulic systems for all major control surfaces, plus a set of drect cable linkages, so even in a fully unpowered glide a true "dead stick" landing is possible. However, this is probably an unfair example as the A-10 was designed in part for extreme survivability in low-altitude combat conditions where the aircraft could encounter practically everything that airplanes and their pilots don't like, from small-arms fire and flak to short-range ground or air missiles and even a well-aimed tank or artillery round.

"Modern" fly-by-wire jets typically have similar redundancy, but with no direct mechanical link from stick to control surfaces, they are at least partially dependent on electrical power for the flight control computer (in addition to the power required for the hydraulic motors). In the case of a total loss of electrical power, you're right, the aircraft would be uncontrollable until one of two things happened; the pilot got one of the electrical sources back online (typically an engine-powered generator), or he gave up and punched out.

One might wonder how much has to go wrong for the generator coupled to each engine turbine and the APU to fail, leaving the pilot with only battery power for the displays (and to attempt maybe one engine restart). The answer is "a lot"; the most likely scenario causing a simultaneous failure of all generation systems is a missile impact, and in that scenario most fighters wouldn't make it back anyway. However, a failure in the power distribution system of the aircraft might be more likely; this system is redundant as well, but there are some necessary bottlenecks, and one or two relatively minor failures in series could conceivably disable a plane mid-flight.

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    $\begingroup$ Only 25 years old? According to Wikipedia, it was introduced in 1977. That makes it 38 years old! $\endgroup$ – Fred Larson Apr 27 '15 at 19:23
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    $\begingroup$ Damn my mental arithmetic. Editing... $\endgroup$ – KeithS Apr 27 '15 at 19:34
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    $\begingroup$ To be perfectly fair, depending on your point of view, the A-10s flying now are only 10 years old at the oldest; the A-10C was first flown in 2005, and is arrived at via a combination of the A-10 SLEP replacing the wings and other fatigued airframe members of older A-10As, plus the PEUP program to upgrade the avionics to a glass cockpit with the capability to fire the latest GPS-guided munitions. Despite the cockpit upgrade, the A-10s retain their triple-redundant flight linkages. $\endgroup$ – KeithS Apr 27 '15 at 19:43
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    $\begingroup$ When being attacked by an A-10 a tanker can greatly improve his chances of survival by standing up in the open turret hatch and flipping the bird at the incoming A-10. This may cause the pilot to laugh so hard he'll twitch the stick a bit and miss the target... Oh, BTW, and in case you've forgotten - the F-35 is The Answer. The only question is, to which question..? $\endgroup$ – Bob Jarvis - Reinstate Monica May 22 '15 at 11:57
  • $\begingroup$ Running out of fuel would seem to do the trick, as well. Can't run the engines or the APU without it... $\endgroup$ – Sean Jul 29 '18 at 0:03

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