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Fatback

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

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I'm having a problem with my PMDG 747 busting the 250kt speed restriction. The AP is reducing thrust and raising the pitch in an attempt to meet it but many times seems to bust it by a few kts before settling back to 250kts. My question for controllers is whether this is acceptable or common in the RW. Thanks!

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Not a problem.

 

Several years ago they were actually testing something like 280 under 10k.  And from what I remember one controller said he really didn't care and would as needed tell you a speed to maintain.  Granted intercepting a localiser becomes much more difficult, so you'd probably want a better speed by then. 

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No big deal if it´s only a few kts.  Maybe you just have to plan your descent a little earlier, or put some restriction in before 10´000ft to be sure.  In real world, at least in Europe, the speed restriction is much higher under 10´000ft unless the airspace is very busy, same for the departure phase.

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This on departure. I know that if a 747 if fully loaded you can get clearance many times to exceed 250kts because your minimum clean manouvering speed is higher than 250kts. Otherwise you'd have to keep some flaps engaged until you reached 10k. But in a relatively light 747 that doesn't "need" to exceed 250kts is it ok and/or common to exceed it by just a few knots when ascending? 

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Yes, perfectly normal and acceptable.

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In busy airspaces they might care but it's hard to notice a deviation of your IAS.  What we see on the radar is ground speed (essentially your true air speed with wind correction)..

 

There's no way they'd really notice a few kts here and there...

 

Where I work (not busy airspace), pilots bust the 250 kt rule all the time.  We don't mind, get's them in faster.

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What would the airline itself think? All airline aircraft now have data recorders that the airline monitors and an overspeed below 10k would surely trigger an alert of some kind. Would the airline worry about a small overspeed? However small, it is still a breach of regulation. 

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Yes the data is recorded however it is not going to be flagged because it is not a big deal. Airlines come down hard on altitude busts, not meeting stable approach criteria, reasons for a missed approach, things that are actually dangerous, not going over 250kts indicated by a few kts whilst on the SID or STAR.

 

As mentioned above, ATC normally want you out of there airspace as quickly as possible and will often give you high speed if available. If they want you at 250kts IAS 220kts or whatever speed just do your best to keep within that range.

 

Next time you are flying the STAR at exactly 250kts Indicated take a look at your ground speed and TAS on the ND, you are not actually flying 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.

 

What you hear of may be the deleting of a Departure speed restriction, or even a STAR restriction when traffic is light.  IF ATC in the US is allowing non authorized aircraft to violate the 250 kt rule, then they too are in violation.

 

The ATC facility and pilot may find themselves explaining "why". 

 

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Yeah this gets discussed to death all over the Internet. Simple fact is thousands of heavy commercial aircraft depart US airfields with a gross weight that gives them a minimum clean speed above 250kts, they are not keeping slats and flaps out all the way up to 10k.

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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.

 

What you hear of may be the deleting of a Departure speed restriction, or even a STAR restriction when traffic is light. IF ATC in the US is allowing non authorized aircraft to violate the 250 kt rule, then they too are in violation.

 

The ATC facility and pilot may find themselves explaining "why".

 

 

This is all good theory and I agree with you... But the practical side and what really happens is different to your post here.

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All I can say is that there's plenty of aircraft that break that limit out there. Most of the time you can just fly either "free speed" or "280 knots" depending on the day, if they want you slower they'll tell you, and no pilot is going to keep the flaps and slats out to 10,000' just because of the 250 below 10 rule.

 

Regards,

Ró.

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Well, it's not theory, it's an FAA rule.  You must maintain your assigned, or obligatory speed within 10 kts or face a possible violation.

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Well all I'll say is practically every pilot who's flown a heavy jet out of the states has a violation then, those  of us who've been flying out of there for years will have hundreds.

 

The phrase: "It's the spirit of the rule, not the rule itself that counts" comes to mind here.

 

Regards,
Ró.

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Well, it's not theory, it's an FAA rule. You must maintain your assigned, or obligatory speed within 10 kts or face a possible violation.

Hey Jerry, we get what your saying regarding the rule. Do you think the bulk of all these heavy jets departing US airfields as we type are not flying their clean speed? Do you think they keep their slats out to maintain 250kts? Just curious.

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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.

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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.

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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.

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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".

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

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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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