To burn or not to burn

[chunder27]

Watching a few geeky fighter jet takeoff videos earlier.

Seems odd that some types always use reheat to take off, others sometimes do and some rarely do.

Seems stuff like Tornado, F16, Mirage 2000 always use it and older stuff obviously.

But Typhoon, sometimes doesn't, nor F18 and one or two others. And the new stuff like JSF and F22 sometimes doesn't either, I know the 22 has a massively powerful engine which would explain it.

This must simply be power to weight, using tanks etc, but do some planes HAVE to use it to take off? I have rarely seen a Tonka take off without it? I guess a B1 or bigger stuff like a F111 could not either.

[StreetDragster]

Runway length and wind strength/direction is maybe a factor on any given take off.

Matt

[frodo_monkey]

There’s a variety of speeds to calculate during your take-off roll (caution, my experience is limited to Tornado - other aircraft types are available!). Tornado needed reheat to get airborne - either max reheat if clean or with small tanks and no external stores, or (more likely) full combat power.

We used a laptop-based programme to calculate the takeoff speeds based on fit, fuel, loadout, temperature, prevailing wind, runway slope, cables etc. This gave us a list of about 7 different speeds:

vGo - speed at which you could continue to safely get airborne if one engine failed
vStop - speed at which you could safely stop using all the runway available
Emergency Max Braking Speed - speed at which you could apply the brakes and get to zero knots by using every last bit of braking available
vStopRHAG - speed at which you could brake then drop the hook, hitting the RHAG (arrestor gear) at max speed
vRHAG - max cable entry speed
vRotate - speed at which you rotated to get airborne.

(It’s been a few years, these definitions are very rough!)

Essentially we took all these on our knee boards, briefed them as part of a pre takeoff brief, and used them to make appropriate decisions if anything happened during the takeoff.

[frodo_monkey]

Basically depends on power/weight influenced heavily by external stores, outside air temperature and wind.

[Tony1963]

frodo_monkey said:

Tornado needed reheat to get airborne - either max reheat if clean or with small tanks and no external stores, or (more likely) full combat power.

Times must’ve changed. A lot!
In my time on Tornado, use of Combat meant a very likely double engine change upon the aircraft’s return.

[J4CKO]

Isn't part of the calculation because you can ?

[aeropilot]

chunder27 said:

Seems stuff like Tornado, F16, Mirage 2000 always use it and older stuff obviously.

Not all older stuff.....

Lightning F.3 and T.5 could take off in cold power only.

The F.6 with the same engines, but a heavier beast, had to use re-heat.