Fighters and ATC: airspeeds

[Nealius]

I can't find a whole lot on how fighters work with ATC in terms of airspeed. I've dug through a few USAF procedures docs for airbases like Kunsan, Incirlik, Shaw, Hill, etc. but they aren't specific on airspeeds. I assume there's some kind of standard taught/written elsewhere. Occasionally on charts I'll see a note to not exceed 250kts, but that's pretty slow for a fighter, especially one carrying a warload. Also considering AB takeoffs, to not exceed 250kts in DCS I have to cut AB almost immediately after gear up.

 

So how does ATC manage fighters' airspeed? Are there allowances so fighters can AB takeoff straight to 350kts departure? What about approaches for the overhead pattern? The overhead should be 350kts from initial, but surrounding airspace might have a "do not exceed 250kts" notice, so how does that work?

[Cab]

I can only speak for the U.S., and it has been many, many years, but this is what I remember:

 

Below 10,000 feet MSL do not exceed 250kts or the minimum speed to maintain safe flight

ATC can allow higher speeds

If you can't maintain 250 you must inform ATC

Within 5 miles of the tower and below 3000? feet, local rules apply (for example the break)

 

Like I said it's been a long time, but I think that pretty much covers it.

[Nealius]

Ahah, that explains why all the USAF procedures say to start the initial from 5nm out. It would seem really hard for wingmen to maintain position when accelerating from 250 to 350, though.

[Cab]

It would seem really hard for wingmen to maintain position when accelerating from 250 to 350, though.

 

Not really. It isn't as hard as it might seem once you've practiced a little.

[ScopeDope]

I am a current FAA controller, former USAF at Holloman AFB (WSMR). The 250kt restriction is essentially waived for fighter aircraft. I can't point you towards it in writing, but I remember there was some document essentially saying its required for flight safety or some such. The T-38s were the most obvious offenders. Trying to sequence ILS with them and anything else is quite a hassle.

 

The best example of the high speed exception is VR / IR routes (low level).

 

Either that or it's just an unspoken rule that nobody really cares how fast you're going when you have a radar on your plane :D

[Nealius]

That waiver rings a bell, so I did some searching and found the FAA agreement with the DOD that lists 6 conditions where military aircraft are exempt from the airspeed regs. Looks like each individual aircraft gets waivers too.

[Ourorborus]

I'm a former raaf controller and now civilians an regulator. In Aust 250 below A010 stands for all. Military for the most part follow the same rules as civvies. Except when in restricted areas designated for training where ATC doesn't play.

 

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[Alpha]

As mentioned military fast jet are waived from the 250kts below 10k ft speed limit (also true in Australia. Check AIP Vol 1). Never heard of a state where this wouldn´t be the case. Most military fast jet dont fly well at 250kts (rather sluggish in comparison to 300 and above) and it´s actually more safe to fly faster.

[Dangerman]

From a UK perspective  based on RAF fast jet operations, 250kts below 10000ft is waived.  
The “low flying handbook” which is a rule book rather than an aide memoire  as its name suggests gives speed limits. If I recall correctly this was about 540kts for low level training including OLF heights at 100ft AGL ....  Back in the day we would use 480 or 540 kts for target runs on the mighty Tornado..

 

the use of reheat in the UKLFS (Uk low flying system) is prohibited except for emergencies or essential training requirements ......which is the get out of jail free card for the boys getting their photo taken in the Machynlleth loop with the orange fun carrots lit.

 

lots of DCS players flash around everywhere with their hair on fire  because they believe that’s what fast jet pilots do.  Not always the case.  If you are a Brit You should be aiming to fly low level cruise at 420kts, anything above about 2000ft agl at around 350-360 kts. Medium to Hi level cruise around .73-.8 Mach.  Tornado didn’t like being to quick in the hi level cruise because the Mach buffet meant you would need to sweep the wings. At .75, you would get Mach buffet which always served as reminder to move the wings back... problem was the release to service allowed 3 wing sweep positions (4 positions if you include 63 sweep when 2250 underwing tanks were fitted). But fortunately, the document didn’t say how quickly, or slowly you would transition them to the new swept position.  By trial and error most discovered that 33 sweep gave the ideal AOA/Mach no/ fuel flow combo.  We would use a specific set of AOA for range or endurance flight. 
 

RTB through initials would be at whatever speed was briefed or was SOP.  Generally between 350-450 kts at a height that wouldn’t get you an interview with the boss/staish.  Joining at 350 kts at 1000ft circuit height was considered as a “normal” join, and not a run in and break. Speed control on the Run in for the break wasn’t essential.. the secret is to be somewhere in the ballpark and not mess about with power to catch a speed otherwise you piss off your mates in close formation on the wing with you shifting the throttle about.  Descending from initials to your break height is a good way to accelerate because no throttle movement needed and your wingmen accelerate with you.

 

on take off, reheat cancelled around 250kts in a tornado, maybe higher if you had proper bombs and warload on the jet. Accept you need to accelerate to speed.  Every second you are in burner is cutting your range a SIGNIFICANT amount.  Just because you have burner, you don’t need to use it all the time.  When you expect your mates to fly in formation , don’t be at 500kts, you are pissing fuel out of the jet very quickly, the jet is more twitchy and you have reduced the catch-up margin that your wingman needs to join formation.  ..........Is the reason I don’t fly much on public servers with strangers.

 

final point on speed/power is when climbing etc at max power, lead has a few percent less than max to give wingmen some flex and ability to catch up.  Same works for descents.  Don’t go idle in the descent and expect wingmen to be there in either the closer  tactical formations or in close formation. Different drags and weights will mean you are not matched.  SOP for us was 80% power with airbrake for a close formation descent to steepen descent but give wingman leeway on power so he can go idle to avoid getting in front of you.  A wide formation descending into low level is ok for idle  as spacing isn’t so critical.

 

wrote a lot more than I intended there but some thoughts on speed whilst flying your pointy jet.

[El Chapo]

Quote

  If you are a Brit You should be aiming to fly low level cruise at 420kts, anything above about 2000ft agl at around 350-360 kts. Medium to Hi level cruise around .73-.8 Mach

 

You have to make a difference between "peace time rules" and "real ops". 

At home (since most conflicts take place abroad nowadays) we strictly stick to local rules and regulations, even if they are not consistent with our training needs. 

In real operations, you choose the flight parameters that suit best to your given task. 

 

Eg: 420 kts for low level is nice, but when going for the real strike (Desert Storm) it was more like 540 kts. 

We used to say that on "D-day" there would be only one throttle position : full forward (let's say 98% to leave a 2% margin to the wingies).

 

Regarding medium or high altitude, flying below Mach 1 is required peace time to avoid unbearable insurance fees... But once you are in for the fight don't expect anyone to push slower, unless if they are physically unable to (Tornadoes or anyone with big tanks or bombs). 

 

You have then 2 options: pushing at the slowest player's speed, or putting the slowest at the rear of the COMAO. 

 

Regarding 250kt rule below 10000', this is a general aviation IFR rule. 

Some countries have specific military rules, where these limitations do not exist. 

 

And eventually, some planes will avoid flying too slow to keep the opportunity to make emergency in flight start up.

Eg: M2000 will avoid flying below 300kt in medium and high altitude, and below 400kt for this very reason.