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The startup process in many military aircraft is, complicated, to say the least.

It takes a lot longer than most would think. An F-16 from cold is required to be able to scramble within 5 minutes if on alert (armed, fueled, and pilot ready), 15 minutes if not.

I also know that during the Cold War when the situation was expected to deteriorate, they could deploy B-52's to all runways (civilian airports included) that were longer than 9,000 feet, just sitting there with engines running ready to go. (Terrifying to think about...)

I also found this:

Default NATO QRA alert time is 15 minutes (in DEFCON 5), although the local CRC can lower that to ten (DEFCON 4), five (DEFCON 3) or even two minutes (DEFCON 2) depending on current state of affairs.

At 5 minutes (DEFCON 3), the engines would be running idle 24/7, at 2 minutes (DEFCON 2) there are pilots in the cockpit 24/7.

Anyways, an F-16 can scramble in 5 minutes. But an F-22 has an automated start process. IIRC, the checklist is something like...

  • Master Switch On.
  • Throttles Forward to idle.

I understand that this may be classified, but I was wondering if anyone can put me in the ballpark.

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    $\begingroup$ Why would that affect scramble time? Is the startup time mostly determined by how long it takes a human to flip switches, or by how long it actually takes things to happen (especially at that speed)? $\endgroup$
    – cpast
    Nov 15, 2014 at 1:21
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    $\begingroup$ @cpast One would assume that if the pilot's attention could be diverted elsewhere during an automated startup, that the entire process would be faster, and more could be simultaneously accomplished. $\endgroup$
    – Rhino Driver
    Nov 15, 2014 at 2:09
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    $\begingroup$ In the military, if its a no-kidding scramble, the normal checklist will not be followed, and you can guarantee that the pilot will be strapping in while the jet starts and getting his aircraft moving as expeditiously as possible. Furthermore, the F22 automatically performs the BITs and runs through the checklist on its own. $\endgroup$
    – Rhino Driver
    Nov 15, 2014 at 2:49
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    $\begingroup$ @SHAF There's a description of a scramble here: historycommons.org/entity.jsp?entity=heather_penney_garcia Penney Garcia, who is a rookie pilot, will later say: “I’d never scrambled before, I’d never done this. I was screaming to the maintainers to pull the chocks, and the guys were pulling the pins to arm the guns. We were going without INS [inertial navigation system].” Sasseville and Penney Garcia are airborne about six minutes after reaching their jets. $\endgroup$
    – ChrisW
    Nov 15, 2014 at 13:32
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    $\begingroup$ Reminder that comments are not for extended discussions, especially about matters not directly related to the question. $\endgroup$
    – raptortech97
    Nov 17, 2014 at 3:09

4 Answers 4

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For military aircraft on "alert", there is a position called cocked on (or as some news sites call it, "hot-cocked"). This procedure is run before the aircraft is placed on alert, and does a pre-flight check of all the instruments and then places them in a state that allows power application in a rapid manner. This way, only minimal steps are required for the aircraft to be ready. In addition to cocking on the aircraft, they can be parked in special areas (some are called Christmas Trees because of their appearance). This allows the aircraft to reach the runway quickly. Also, in the old SIOP days, there was an Alert Facility near where the aircraft were parked, where the crew would stay in a state of readiness.

An Alert Christmas Tree

Currently the full SIOP mission isn't active (it was ended in 1992 by President Bush, but there are still forces dedicated to it in a new capacity). However, the facilities still exist on many bases. They can use these facilities still for whatever alerts are required.

With an aircraft in cocked on position, with a pilot on alert (cockpit or facility), an aircraft can take off in a very, very short time (from seconds to minutes). In general, the mission requirements will dictate the amount of time that the pilot is given to take off (as you note in your question). So sadly, I can't give a specific answer to your question, because it depends on parameters you haven't specified.

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You can start an f-22 in about 2 minutes or less. The procedure is

  1. Master Batt.
  2. APU(Auxiliary Power Unit)
  3. Flip 2 generator switches
  4. flip nav and position lights as required for mission
  5. Make sure fuel switches are set right
  6. Wait a couple seconds for APU to finish start up
  7. push throttles to idle
  8. configure MFDs as needed as engines spin up.
  9. taxi to runway
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    $\begingroup$ Welcome to aviation.se. Would you happen to have any source? $\endgroup$
    – Federico ♦
    May 10, 2016 at 7:28
  • $\begingroup$ Yeah running the flight sim made by IRIS which was done for Prepar3D for Lockheed with their oversight. That is the process I go through to get the jet up and running from a cold dead start. I am sure the pros can do it way faster than me. And I am sure the MFDs are probably set up the way the pilot likes from the get go. $\endgroup$
    – Donald
    May 16, 2016 at 7:51
  • $\begingroup$ You could setup the lights on the ground roll. or while on climb (if procedures allow). To gain 3-4 more seconds. $\endgroup$
    – Gürkan Çetin
    May 24, 2017 at 19:05
  • $\begingroup$ That’s not an acceptable or reliable source. $\endgroup$
    – Carlo Felicione
    Aug 17, 2018 at 23:49
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There is no set time because there are too many factors. On a large airfield it could take more than 5 minutes just to taxi to the runway. If you maintain a plane on alert (expensive and time consuming), you could get it rolling inside of 5 minutes. That means:

  • The pilot is fully ready and has all his stuff ready to go; literally waiting to jump into the plane

  • The aircraft has been pre-flighted, fueled and is on the apron ready to go

  • Munitions have been loaded and checked

Needless to say, keeping aircraft in this condition is expensive and I would imagine is only done at certain specific airbases where some special need for a fast launch is required. Loading and unloading weapons is a very time-consuming process and there is a lot of red tape associated with it.

The time constraints have nothing to do with the type of aircraft. It's more a question of the human factor and lots of little things.

Also, another factor is how much you are willing to skip. You might have a 40-point checklist and 25 of them are "optional" items that pertain to safety. If you don't care about dying, feel free to ignore them and you can take off 5 minutes faster.

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    $\begingroup$ I think the original question is geared away from aircraft on alert, and specifically more towards aircraft that are scrambled to meet a surprise threat (like on September 11th). Furthermore, certain aircraft are much easier to start and get airborne, and if its a matter of life and death, nobody is going to follow a complete checklist. $\endgroup$
    – Rhino Driver
    Nov 17, 2014 at 23:22
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As some other answers have mentioned, and some haven't, it varies very widely by readiness - whether the aircraft was expected to need to scramble.

The usual time for an aircraft to scramble in modern wartime would be 15 to 25 minutes. This is from normally maintained readiness, for a typical post-cold-war conflict. This figure came from a flight line ops Lt.Col (not a pilot, the guy responsible for getting planes ready to fly), unofficial, but it aligns well with other information.

Newer aircraft are not much faster to start, since the steps are the same, and pilots know them; automation just simplifies it. There's still more to it than just one switch. The Chegg answer (hardly a place for such info) that seems to have been quoted in the question is not correct.

Engine ground running can be appropriate when an attack or a major war is expected. Running aircraft can't be refueled, the pilot can't leave the cockpit, and parts run up the hours, so very few planes can be kept in such a condition. Given how few F-22 exist at all, the US could realistically maintain 2-4 flights at such a readiness level.

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