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Fatback

250kt under 10k restriction. Any RW controllers out there?

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Ronan, thanks for the feedback. If your aircraft is heavy I assume the higher minimum clean maneuvering speed would require either ATC clearance to ascend through 10k at a higher speed or you would have to use some flaps to increase the clean maneuvering speed and thus burn more fuel because of the increased drag. 

 

But what about "accidental" overspeeds on the ascent. You're in the cockpit at say 6k AGL and you're approaching 250kts but don't need higher because your clean maneuvering speed is say 220kts. As you're nearing the speed restriction you can see your N1 decreasing and your nose coming up and the rate of speed increase is slowing. But at about 245 kts it becomes clear that you're going to bust your minimum by a few knots, say to 253 or 255 kts, but it's also clear that it is going to drop again to 250 kts. Would you take off the auto pilot and raise the nose to reduce speed and not bust the limit or just let the AP continue knowing that it was under control but was going to bust the limit a little bit before it settled back down to 250kts?

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Contrary to a very widely held opinion, ATC in the United States is not authorized to waive the 250-knot limit below 10,000 feet. Apart from special conditions, flights that wish to exceed this limit (as for airshows) must obtain a waiver directly from the FAA for the flight, the event, or the facility. The military has a standing waiver from the FAA for certain flights under certain conditions.

You are correct in that an ATC controller cannot, on his own authority, waive the speed restriction for any aircraft.

 

However, in the U.S., FAR 91.117 (which is the where the 250 knot restriction is defined) has an exception in paragraph 'D' which states that if a given aircraft's minimum safe airspeed is higher than 250 knots, then the aircraft may be operated at the higher speed. This would typically apply to a 747 at maximum takeoff weight.

 

An aircraft operating under these circumstances does NOT require the permission of ATC to exceed 250 knots. The choice of airspeed is entirely up to the pilot in command. The pilot may (if he wishes) inform the controller of the higher speed as a courtesy, but he is not required to do so, and the controller can neither approve, nor disapprove the higher speed. The pilot of a heavy transport-category aircraft cannot (and will not) be cited by the FAA for exceeding 250 knots below 10,000 as long as the aircraft's performance envelope at a given weight requires the higher speed.

 

In many European countries individual ATC controllers DO have the authority to waive speed restrictions for any aircraft if conditions allow.


Jim Barrett

Licensed Airframe & Powerplant Mechanic, Avionics, Electrical & Air Data Systems Specialist. Qualified on: Falcon 900, CRJ-200, Dornier 328-100, Hawker 850XP and 1000, Lear 35, 45, 55 and 60, Gulfstream IV and 550, Embraer 135, Beech Premiere and 400A, MD-80.

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Ronan, thanks for the feedback. If your aircraft is heavy I assume the higher minimum clean maneuvering speed would require either ATC clearance to ascend through 10k at a higher speed or you would have to use some flaps to increase the clean maneuvering speed and thus burn more fuel because of the increased drag. 

 

But what about "accidental" overspeeds on the ascent. You're in the cockpit at say 6k AGL and you're approaching 250kts but don't need higher because your clean maneuvering speed is say 220kts. As you're nearing the speed restriction you can see your N1 decreasing and your nose coming up and the rate of speed increase is slowing. But at about 245 kts it becomes clear that you're going to bust your minimum by a few knots, say to 253 or 255 kts, but it's also clear that it is going to drop again to 250 kts. Would you take off the auto pilot and raise the nose to reduce speed and not bust the limit or just let the AP continue knowing that it was under control but was going to bust the limit a little bit before it settled back down to 250kts?

No, just leave it be, if you looked like you were really going to break the limit, you'd advise ATC. It all depends on the situation, some airports at certain times of the day couldn't care less what speed you're going at, some airports don't mind within say 20 knots, and then there's some where you really have to be on the dot. Experience comes in here. Often times if a situation like that does arise it's a judgement call, at some places going 260 is fine, some places I might advise that we were slightly fast and at other places I'd make sure it didn't happen.

 

As mentioned above, controllers read Ground Speed, so they can't tell really what speed we're doing within reason.

 

Regards,

Ró.


Rónán O Cadhain.

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Removed accidental double-post...<br />


Jim Barrett

Licensed Airframe & Powerplant Mechanic, Avionics, Electrical & Air Data Systems Specialist. Qualified on: Falcon 900, CRJ-200, Dornier 328-100, Hawker 850XP and 1000, Lear 35, 45, 55 and 60, Gulfstream IV and 550, Embraer 135, Beech Premiere and 400A, MD-80.

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Ronan, thanks for the feedback. If your aircraft is heavy I assume the higher minimum clean maneuvering speed would require either ATC clearance to ascend through 10k at a higher speed or you would have to use some flaps to increase the clean maneuvering speed and thus burn more fuel because of the increased drag. 

 

But what about "accidental" overspeeds on the ascent. You're in the cockpit at say 6k AGL and you're approaching 250kts but don't need higher because your clean maneuvering speed is say 220kts. As you're nearing the speed restriction you can see your N1 decreasing and your nose coming up and the rate of speed increase is slowing. But at about 245 kts it becomes clear that you're going to bust your minimum by a few knots, say to 253 or 255 kts, but it's also clear that it is going to drop again to 250 kts. Would you take off the auto pilot and raise the nose to reduce speed and not bust the limit or just let the AP continue knowing that it was under control but was going to bust the limit a little bit before it settled back down to 250kts?

Fatback, you really need to stop worrying about minor speed excursions. Have a reread of the thread. Disconecting the A/T or A/P because of a few knots over 250kts indicated is not required. If the automatics are not behaving as expected then yes you take over manually, a minor fluctuation is completely normal.


Rob Prest

 

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Ok guys, slow down.  I eluded to exceptions in the first statement.  Most of us are really saying the same thing here.

If the B747 is on the approved list then yes he can exceed the 250 kt rule...IF his wt/condition warrants it only.  Many aircraft are on this list, and it is up to the pilot to know if he is flying one.  And yes, it is not (at the moment) a rule that the pilot advise the controller if he exceeds this speed if authorized to do so, but that is being considered for revision as we type.

If you exceed the speed it should be either authorized, or necessary.  Necessity would require notification of ATC.  Be advised that necessity is not a lazy pilot who doesn't want to pull the speedbrake handle because he already did something wrong.  ATC, on it's own volition, can not bust this regulatory speed restriction.

One of the problems is pilots busting the speed because they are in a 747 when they know their wt/conditions do not legally warrant the exception.

The reason for the rule is flight safety.  Not only for the aircraft in question, but all the other aircraft in the area...collision avoidance...be it other aircraft or birds etc.  Not all aircraft are being controlled by ATC, and not all aircraft show up on radar.

I had a radome break off in a hail storm years ago and had to exceed the speed and a simple call to ATC was all that was needed.  ATC is there to work with you, but violate you they will if you bust regs without a good reason.

Time to but this discussion to bed.  Good night all.

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I agree with Ronan, controllers cannot see what your IAS is, and the restriction is on IAS.

 

You would have a fair idea of what 250 knots looks like, but then you have different aircraft types, winds etc to contend with. Do you think a controller is glued to the screen checking that your ground speed is somewhere around the 250 knots? It is just not possible.

 

If you see an aircraft return going faster than others in your scope you could ask him what his indicated is and go from there.

 

There is a good entry in ICAO which says something along the lines of " the rules, guidelines and regulations governing Air Traffic Control should not override the use of common sense".


Will Reynolds

 

Flight Sim Addict

 

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Well, the FAA doesn't follow the ICAO rules, nor do they follow the principle of common sense :P


vatsim s3

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I can speak from experience with the U.S. ATC system; what happens elsewhere I cannot comment on...

 

To the OP, if you're talking less than a 10-knot deviation, nobody cares and nobody would notice.  I've been doing this a long time and have never seen anyone get violated for it. 

 

On departure, we expect the 747 and a few others (the Concorde comes to mind, but that was ages ago!  Am I that old?) to need to be faster than 250 below 10,000, but this is not usually so on arrival, where being faster than 250 below 10,000 would be highly frowned upon.  And it's true we cannot see your airspeed, but when you work jet after jet over the same route in a short period of time, you quickly recognize an off-speed airplane.  Usually, it's the Airbus that slows down sooner than you'd like. 

 

In commercial and corporate jets, today's crews and avionics are quite precise, and accidental deviations of this sort are very rare in my experience.  I know in the analog jet days, quite a bit of fudging went on descending through 10,000.

 

It is correct that in the U.S., ATC cannot approve deviations to the FAR, but nor do we disapprove the rare request.  Airplanes that need to go faster for whatever reason simply do so without much fuss.

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