The lovely F-86 Sabre always seems to have its speedbrakes deployed when parked, to the point that most of the results I found looking for a good photo for this question were scale model forums debating the exact angle at which to position them.

F-86F Sabre s/n 52-5276 (buzz no FU-276), 36th FDW (36th Fighter Day Wing, USAFE) at Soesterberg/Netherlands, Nov. 9 1954. S/n 52-4725, -4670 (or -4679) of 81st FBS is assured at Giebelstadt AB in 1953. (Source)

However, none seem to offer more than wild speculation about why they drop. The guesses mainly fall either into "it's held up by hydraulic pressure, so they fall down when the hydraulics are off" or "it doubles as a maintenance access door for some kind of ground servicing"... but with no evidence either way.

Interestingly, the FJ-2/FJ-3 Fury carrier derivative seems to not have had this quirk, even though my limited knowledge is that the changes were mostly just in the wing and landing gear. U.S. Navy North American FJ-3 Fury fighters from Fighter Squadron 173 (VF-173) "Jesters", on the flight deck of the aircraft carrier USS Saratoga (CVA-60), 1956-1957. VF-173 was assigned to Carrier Air Group 17 (CVG-17), which was assigned to the USS Franklin D. Roosevelt (CVA-42) from 1956 to 1958. (Source)

It also looks like the F-86D Sabre Dog and its descendants parked with the speedbrakes stowed, although that was a different fuselage design.

So my two-part question is:

  1. Did the speed brakes dropping open when the F-86 was parked serve some intentional function (such as servicing or inspection access), or was it just that they didn't have a mechanical lock to hold them up?
  2. Which of the many variants/derivatives of the Sabre had the droopy speedbrakes?
  3. For bonus points, what was changed to keep the speedbrakes up on variants like the Fury, and why?

1 Answer 1


The F-86 Sabre Pilot's Flight Operating Manual is availlable on Google books site.

It describes the speed brake system as being operated by the utility hydraulic system. Both extension and retraction are hydraulic, and the operating switch also has a "neutral" position, which locks the speed brake into its current position by inhibiting hydraulics flow. The neutral position is to be used whenever the desired position (open or closed) is reached to minimize fire hazard, as the hydraulic lines are placed close to the engine. The speed brakes do not have mechanical locks. Emergency closing is provided by a swich which depressurizes the actuators allowing airflow to close the speed brakes.

The reason for the speed brakes being open while parked is simply that the manual states in the "Stopping Engine" checklist item 5: "Speed brake switch - out". The manual does not elaborate on why the speed brakes are selected out for parking.

The carrier derivate obviously has different checklist omitting the speed brake-out item.

The speed brakes being open while parked does give the pilot (and mechanics) the possibility to externally inspect the system (hinges and such) before flight, and verify the operation (closing) without fully cycling the system during preflight check.

  • 7
    $\begingroup$ Preflight check might also include things like "Check for bird's nests inside speed brakes". Seems like it'd be a tempting nook for some feathered creatures. I have to assume that's happened at least a few times, especially if a plane has been sitting around for a while... $\endgroup$ Commented Aug 18, 2022 at 13:47
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    $\begingroup$ Love the illustrations in that manual! It does mention "dump utility hydraulic pressure by operating speed brakes" after that checklist item 5 - I would imagine that dumping pressure "safes" the system (for servicing, and reducing chance of hydraulic leaks near the hot engine), and the speed brakes are just a convenient way to do that. I'll leave this open a little longer in case someone wants to chime in why the Fury had a different procedure for the fake bonus points. :) $\endgroup$
    – CameronSS
    Commented Aug 18, 2022 at 18:53
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    $\begingroup$ The manual or procedure or authorities or law or whatever states so is never a REASON. That is the QUESTION: why the manual states what it states. $\endgroup$ Commented Aug 19, 2022 at 8:06
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    $\begingroup$ @Jpe61 I don't think the question is really asking "why do the pilots open the speed brakes" (to which the answer is obviously "it's in the checklist"). The question is interested in the purpose of opening the speed brakes: i.e. "Did the speed brakes dropping open when the F-86 was parked serve some intentional function". That the checklist says to open the brakes is evidence that there is a purpose (or why was that step written into the checklist), but leaves unanswered what that purpose is. This question is the "Why PFOM commands air brakes out" one you acknowledge as valid. $\endgroup$
    – Ben
    Commented Aug 19, 2022 at 9:19
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    $\begingroup$ @Jpe61 while that might be good advice for pilots it's poor advice for aviation engineers. Someone has to write these things. $\endgroup$ Commented Aug 19, 2022 at 19:33

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