ATC-directed speeds

[airguy]

First - I'm not an IFR pilot (though I do intend to start very soon) and I don't fly anything with enough power to get this direction from ATC.

Saturday I was flying between KSJT and KMAF and heard Ft. Worth Center direct an airliner descending into Midland to "reduce speed to 280 knots". It was an airliner callsign and so they were obviously on an IFR plan, I know I've heard this type of direction many times before - but the question occurred to me on this occasion WHAT speed should be reduced? TAS, IAS, or GS?

I don't see that ATC can reasonably account for winds at the differing flight levels, so that would argue for either GS or TAS, but GS could potentially have 80-100 knots +/- depending on the winds aloft. Indicated airspeed is going to be dependent on altitude, so that's fairly vague. Is this a TAS designation?

 

[Velocity173]

Indicated. 5-7-1 in the .65.

 

[jordane93]

it is indicated airspeed

 

[ebykowsky]

And I believe they can do that on a VFR plan as well. I've had a controller tell me to maintain at least 90kts until a certain distance from the airport.

 

[jordane93]

yea ive been told by tower to maintain at least 100 until final so a lear jet wouldnt run into us

And I believe they can do that on a VFR plan as well. I've had a controller tell me to maintain at least 90kts until a certain distance from the airport.

 

[jesse]

First - I'm not an IFR pilot (though I do intend to start very soon) and I don't fly anything with enough power to get this direction from ATC.

Saturday I was flying between KSJT and KMAF and heard Ft. Worth Center direct an airliner descending into Midland to "reduce speed to 280 knots". It was an airliner callsign and so they were obviously on an IFR plan, I know I've heard this type of direction many times before - but the question occurred to me on this occasion WHAT speed should be reduced? TAS, IAS, or GS?

I don't see that ATC can reasonably account for winds at the differing flight levels, so that would argue for either GS or TAS, but GS could potentially have 80-100 knots +/- depending on the winds aloft. Indicated airspeed is going to be dependent on altitude, so that's fairly vague. Is this a TAS designation?

Indicated - just like being told to turn to a heading is magnetic.

 

[coma24]

If it helps, the speeds are assigned for maintaining lateral separation. While the GS will change with a given IAS speed assignment, it will be consistent for all aircraft at a given altitude in a given location.

It's also the only form of speed that all aircraft are capable of following. /A or /U aircraft may not have GS readouts, and working with TAS isn't practical as it's really only computed in real time on glass panels. So, by simple elimination and without knowledge of the 7110.65, IAS is the only practical answer.

 

[airguy]

If it helps, the speeds are assigned for maintaining lateral separation. While the GS will change with a given IAS speed assignment, it will be consistent for all aircraft at a given altitude in a given location.

It's also the only form of speed that all aircraft are capable of following. /A or /U aircraft may not have GS readouts, and working with TAS isn't practical as it's really only computed in real time on glass panels. So, by simple elimination and without knowledge of the 7110.65, IAS is the only practical answer.

Makes sense. The controller doesn't know what the winds are in his block of airspace, and doesn't really need to. As long as they are all using the same measurement it just becomes relative.

At some point higher up I notice they switch to Mach number though, I've heard that call frequently as well, with Center setting spacing.

 

[coma24]

Yes, at FL240 and above.

 

[Velocity173]

Makes sense. The controller doesn't know what the winds are in his block of airspace, and doesn't really need to. As long as they are all using the same measurement it just becomes relative.

At some point higher up I notice they switch to Mach number though, I've heard that call frequently as well, with Center setting spacing.

Mach above FL240.

Generall they know the winds. Before signing on you want to know what the winds are doing to aid in vectoring. If you don't check the winds it'll become quite apparent in a few minutes when you see the effects on aircraft tracks and ground speeds.

Had a Falcon 10 once doing over 360 kts decending out of 6,000 ft. Told him to maintain at or below 250 kts below 10,000 ft. He came back with a snotty "It's indicated and not true!" OK, fly heading XXX for the sequence. Called weather to check winds at 6,000 and it was actually a crosswind with maybe a 10 kt tailwind. Guy was lying.

 

[AggieMike88]

And I believe they can do that on a VFR plan as well. I've had a controller tell me to maintain at least 90kts until a certain distance from the airport.

yea ive been told by tower to maintain at least 100 until final so a lear jet wouldnt run into us

Been told similar by a Tower ("make best speed to numbers") so that they could get me in ahead of a business jet and still maintain adequate separation.

Made me appreciate how quickly a C182 can change from a decent speedster to a 40° flaps out flying brick.

 

[flyingron]

I've been asked if I could maintain a specific speed even VFR while in the class B.

 

[Greg Bockelman]

The controller doesn't know what the winds are in his block of airspace, and doesn't really need to.

Actually, he probably has a pretty good idea. But you are correct on the rest of the post.

 

[48dodge]

Been told similar by a Tower ("make best speed to numbers") so that they could get me in ahead of a business jet and still maintain adequate separation.

My one landing at our local class C airport they had me do that. A little different feel turning onto final at about 115 knots and no flaps. Took a little while to get the plane on the ground

 

[midlifeflyer]

First - I'm not an IFR pilot (though I do intend to to get start very soon) and I don't fly anything with enough power to get this direction from ATC.

Saturday I was flying between KSJT and KMAF and heard Ft. Worth Center direct an airliner descending into Midland to "reduce speed to 280 knots". It was an airliner callsign and so they ere obviously on an IFR plan, I know I've heard this type of direction many times before - but the question occurred to me on this occasion WHAT speed should be reduced? TAS, IAS, or GS?

Let's see... ATC wants you to:

1. Look at your airspeed indicator and make it match the number he gives you.

or


2.

a. Pull out your E6B
b. Change your altimeter setting to 29.92 to get the pressure altitude.
c. Go off frequency to call flight service or flight watch to get the winds aloft.
d. Do the E6B magic to figure out what GS or TAS is.
e. Figure out what IAS will give you that number.
f. Match the number you just spent 10 minutes calculating​

 

[frfly172]

Usually being a smaller airplane I get ,keep your speed up. Both from ATC and the tower controller.

 

[Z06_Mir]

I've been asked if I could maintain a specific speed even VFR while in the class B.

"Keep speed 120 or great as long as possible, B737 5 miles to follow you. clear to land 25L long landing approved"

Probably the most fun I've had flying to date. They climbed me to 4,500 then had my dive-bomb down to airport elevation of 1,200. I was in the yellow arc coming down until it was time for gear & first flaps. It was awesome, and a good experience for maintaining speeds VFR or IFR. I was VFR. You'll make a lot more friends in big places if you're able to (safely) accommodate their requests.

 

[midlifeflyer]

Been told similar by a Tower ("make best speed to numbers") so that they could get me in ahead of a business jet and still maintain adequate separation.

Once even got the opposite. I was IFR flying into KORL in a 172 and asked to slow down for another aircraft doing a practice approach.

 

[JHW]

on a related note i heard the other day:

center: king air 2CF turn 10 deg left for traffic
2CF: CF roger and we're a citation not a king air
center: 2CF is that normal speed for you?
2CF: affirmative
center: oooookkkkaaaaayyy, twin cessna 2CF resume on-course

 

[Palmpilot]

Once even got the opposite. I was IFR flying into KORL in a 172 and asked to slow down for another aircraft doing a practice approach.

If I'm in a 172 landing behind a Citabria, I make sure to allow extra spacing.

 

[35 AoA]

Had a Falcon 10 once doing over 360 kts decending out of 6,000 ft. Told him to maintain at or below 250 kts below 10,000 ft. He came back with a snotty "It's indicated and not true!" OK, fly heading XXX for the sequence. Called weather to check winds at 6,000 and it was actually a crosswind with maybe a 10 kt tailwind. Guy was lying.

Wow, guy must have thought you were born yesterday. How about "sorry approach, I had my head up my butt and forgot to slow down, won't happen again sir". That attitude above is just asking to get violated

 

[Velocity173]

Wow, guy must have thought you were born yesterday. How about "sorry approach, I had my head up my butt and forgot to slow down, won't happen again sir". That attitude above is just asking to get violated

Yeah, had biz jets jets all day long from that area doing around 300 GS speed below 10 grand. This guy shows up going significantly faster so there was no way he was doing 250 indicated at 6,000ft. Truth is, I wouldn't have said a word if it wasn't for the fact I had a Dash 8 doing approach speeds on the LOC in front of him. He cancelled as soon as I put him on a vector to follow. Just a guy impatient and in a hurry to get his customer on the ground.

Hornets, I'd send them to the air station all day long pushing 400-450 kts below 10 grand. If everyone's doing it, there's no sequencing issue and they're outta my airspace faster...which was good.

 

[35 AoA]

Hornets, I'd send them to the air station all day long pushing 400-450 kts below 10 grand. If everyone's doing it, there's no sequencing issue and they're outta my airspace faster...which was good.

We have LOA's to exceed 250 below 10 at most airfields that we normally operate out of (Lemoore, Miramar, Beaufort, Oceana, Fallon), but I think that also leads to a misconception that this arrangement applies at every airfield. There are a lot of guys who think that we have a blanket LOA with the FAA for any airfield in the country, which as far as I know, is not true. Most controllers are cool about it, but more likely than not, that Hornet guy has no idea that he is actually violating a FAR.

 

[Art VanDelay]

Funny you should mention 280 Kts as that's the new speed we're all supposed to do our descents at now. Doesn't matter what kind of Econ speed the box gives you, ATC expects everyone to hard code that speed for after the transition from Mach.

 

[Velocity173]

We have LOA's to exceed 250 below 10 at most airfields that we normally operate out of (Lemoore, Miramar, Beaufort, Oceana, Fallon), but I think that also leads to a misconception that this arrangement applies at every airfield. There are a lot of guys who think that we have a blanket LOA with the FAA for any airfield in the country, which as far as I know, is not true. Most controllers are cool about it, but more likely than not, that Hornet guy has no idea that he is actually violating a FAR.

Wanna say at Beaufort it was 350. Been a longtime though so not sure. I talked about it in the overhead thread how we were given orders to log anyone who was over 350 GS after the initial. Crazy.

Apparently back in the old days at Miramar, they'd put grease pencil marks at a certain interval on the tower windows overlaying the mountains to the east. Start the time from one mark to the next and get their speed. Pilots would get around it by coming in at an angle towards the tower, thereby screwing up the accuracy...fighter pilots.

 

[Captain]

Odd story. I once heard center (Cleveland or Chicago I think) assign an airliner a Ground Speed. She was obviously flustered and probably new but the airline guy, after a puzzled quarry, accepted it. I don't think I would have.

ATC: 'ah, big wings, ah, ah, maintain 280 kts ground speed.'
BW: 'you want us to fly a ground speed??'
ATC: 'ah, yeah, 280 kts ground speed.'

Pause

BW: 'okayyy. 280 ground speed.'

 

[coma24]

Sounds like that controller could've benefited from "reduce speed xx knots"

That way, you don't have to try to guess their current IAS to come up with a new one.

There are lots of ways to assign speed in the .65, but GS isn't one that I'm aware of

 

[airguy]

Funny you should mention 280 Kts as that's the new speed we're all supposed to do our descents at now. Doesn't matter what kind of Econ speed the box gives you, ATC expects everyone to hard code that speed for after the transition from Mach.

That may have been the situation then, because about 3 minutes after that call, Center cleared the flight down to 11,000 and he read back "Leaving seventeen point 4 for 11", so if he had been going down at a good clip he might have been coming out of FL240 when Center gave him 280 knots.

 

[35 AoA]

Wanna say at Beaufort it was 350. Been a longtime though so not sure. I talked about it in the overhead thread how we were given orders to log anyone who was over 350 GS after the initial. Crazy.

Apparently back in the old days at Miramar, they'd put grease pencil marks at a certain interval on the tower windows overlaying the mountains to the east. Start the time from one mark to the next and get their speed. Pilots would get around it by coming in at an angle towards the tower, thereby screwing up the accuracy...fighter pilots.

haha nice......I'd expect nothing else Seriously though, 350 is the norm community wide......much faster and you are just arcing out to like a 3 mile abeam, and much slower and it just gets mushy and you are trying to drop the gear and flaps in the crosswind. I remember being a wingman coming back to Tyndall after my lead and I shot off some sparrows, and though I never looked at the HUD, we definitely had the transonic intake buzz going pretty hard. It was funny because the AF controllers loved the SH cv break, but none of the AF Eagle guys were allowed to do it......300 kts, 2k feet or something absurd like that. So we brought the heat that day (I'm guessing about 6 bills), and I basically was starting my approach turn at the drone way, which is like 3 miles deep on the approach end of the runway if you aren't familiar with that field, it took that long to slow down to the point where I could dirty up. Fun, but really not worth it.

It is actually legit that we should be > 250 its on departure/arrival for a number of reasons (the big one is angle of attack and resultant vis over the nose), but it is silly to say that a guy can't adhere to the FAA limits when going into an unfamiliar civilian field for a straight in. I'd much rather be below 250 and have time to break out that 6 ft chart in a 1 ft cockpit and not goon up a STAR than just rage in blindly and **** everyone off. I'm also a believer that the difference between a 250 kt and a 500 kt break is hardly noticeable to most people. You look fast and cool either way, so you may as well not hang everything out and lose your wings over trying to make an imperceptibly faster arrival.

 

[Velocity173]

haha nice......I'd expect nothing else Seriously though, 350 is the norm community wide......much faster and you are just arcing out to like a 3 mile abeam, and much slower and it just gets mushy and you are trying to drop the gear and flaps in the crosswind. I remember being a wingman coming back to Tyndall after my lead and I shot off some sparrows, and though I never looked at the HUD, we definitely had the transonic intake buzz going pretty hard. It was funny because the AF controllers loved the SH cv break, but none of the AF Eagle guys were allowed to do it......300 kts, 2k feet or something absurd like that. So we brought the heat that day (I'm guessing about 6 bills), and I basically was starting my approach turn at the drone way, which is like 3 miles deep on the approach end of the runway if you aren't familiar with that field, it took that long to slow down to the point where I could dirty up. Fun, but really not worth it.

It is actually legit that we should be > 250 its on departure/arrival for a number of reasons (the big one is angle of attack and resultant vis over the nose), but it is silly to say that a guy can't adhere to the FAA limits when going into an unfamiliar civilian field for a straight in. I'd much rather be below 250 and have time to break out that 6 ft chart in a 1 ft cockpit and not goon up a STAR than just rage in blindly and **** everyone off. I'm also a believer that the difference between a 250 kt and a 500 kt break is hardly noticeable to most people. You look fast and cool either way, so you may as well not hang everything out and lose your wings over trying to make an imperceptibly faster arrival.

Yep, never seen a decent AF break. All the good ones are when the guys have been on the boat too long and they check in at "angels ten" doing 500 kts handed off from FACSFAC.

Even during MOA activation at NBC, all the good attacks were VV/VM. When you see an A-6 or F-14 inbound on radar you go outside to watch because you know it's gonna be good. Had a local Hornet hit supersonic during one attack. Phone was ringing off the hook!

Hey, if you're coming in hot like above at Tyndall, can you still wrench back on the stick and the computer keep it from over stressing?

Sorry to derail the thread. The answer is indicated.

 

[BillTIZ]

Hornets, I'd send them to the air station all day long pushing 400-450 kts below 10 grand. If everyone's doing it, there's no sequencing issue and they're outta my airspace faster...which was good.

A lot of Military aircraft have approvals for greater than 250KIAS below 10K MSL.

Our normal climbout was 300 knts, then 360 knts then transition to .82M, the transition occurred around FL180 on most days. We were allowed, IIRC, 300knts below 10K MSL on arrival. 250 on radar downwind, 240 the flap/gear horn went off.

Of course, low level in the IR, 540KGS.

Edit: the approved speeds are in the back of 7110.65, or at least they used to be when I was in the ATC game.

 

[aterpster]

A lot of Military aircraft have approvals for greater than 250KIAS below 10K MSL.

Our normal climbout was 300 knts, then 360 knts then transition to .82M, the transition occurred around FL180 on most days. We were allowed, IIRC, 300knts below 10K MSL on arrival. 250 on radar downwind, 240 the flap/gear horn went off.

Of course, low level in the IR, 540KGS.

Edit: the approved speeds are in the back of 7110.65, or at least they used to be when I was in the ATC game.

In certain circumstances for civil airplanes, the approval is built into the reg. When the L1011 was at max structural gross takeoff weight we would clean up and climb at 275 KIAS or so. The 747 was even faster departing on a very long trip (LAX-LHR) full of people and fuel.

 

[Velocity173]

A lot of Military aircraft have approvals for greater than 250KIAS below 10K MSL.

Our normal climbout was 300 knts, then 360 knts then transition to .82M, the transition occurred around FL180 on most days. We were allowed, IIRC, 300knts below 10K MSL on arrival. 250 on radar downwind, 240 the flap/gear horn went off.

Of course, low level in the IR, 540KGS.

Edit: the approved speeds are in the back of 7110.65, or at least they used to be when I was in the ATC game.

Sure if you have an LOA or it's for operational necessity / safe airspeed but there is no blanket waiver that I'm familiar with for military aircraft. I've had F-15s ask me if their speed (460 kts) was good for the overhead. I had no authority to authorize anything above 250 kts below 10,000 ft. I suppose operational necessity could be applied liberally in this case but I think it had more to do with announcing their arrival to the Marines.

Generally you just look the other way. Talking to my brother last night he said he was just looking at a B-1 on radar doing 330 kts at 7,000 ft. They have no LOA with the B-1s. As controllers they really don't care. Only people who care are certain commanders and the public. I've pulled the tapes and investigated speeds and altitudes for both cases.

EDIT: just so happens yesterday I was pushing 250 descending to an airport in a Mustang. In this case I'm sure the public wouldn't have minded but the pilot was well aware of the restriction.

 

[roncachamp]

A lot of Military aircraft have approvals for greater than 250KIAS below 10K MSL.

Our normal climbout was 300 knts, then 360 knts then transition to .82M, the transition occurred around FL180 on most days. We were allowed, IIRC, 300knts below 10K MSL on arrival. 250 on radar downwind, 240 the flap/gear horn went off.

Of course, low level in the IR, 540KGS.

If a faster speed is needed for safety of flight reasons then that faster speed is permitted by the regulation. No waiver required, applies to civil and military aircraft. DoD has been issued an authorization to operate aircraft at speeds in excess of 250 KIAS below 10,000 feet MSL within active MOAs and MTRs.


§ 91.117 Aircraft speed.

(a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.).

(b) Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph.). This paragraph (b) does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section.

(c) No person may operate an aircraft in the airspace underlying a Class B airspace area designated for an airport or in a VFR corridor designated through such a Class B airspace area, at an indicated airspeed of more than 200 knots (230 mph).

(d) If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed.

Edit: the approved speeds are in the back of 7110.65, or at least they used to be when I was in the ATC game.

How long ago did you leave the game? I spent 30 years in ATC and never saw that in 7110.65.

 

[35 AoA]

Hey, if you're coming in hot like above at Tyndall, can you still wrench back on the stick and the computer keep it from over stressing?

Sorry to derail the thread. The answer is indicated.

Yes and no. The G-limiter works as advertised provided you don't apply G so quickly that it can't keep up. Most of the time that is hard to do. That said, there are some flight regimes where it is pretty easy if you aren't careful. I've pulled 8.9 (nominal 7.5G limit) and over-g'd in a defensive break turn down low without a lot of gas weighing me down. That is where you will typically see it. A guy slams the stick back into the lap to max perform, and doesn't realize how fast they are going, and down low and light, the controls are effective enough to give it to them. Same would apply for a really SH break, provided the pilot was super aggressive. Using the same stick input you would use for a 350 kt break at 600+ would probably snatch the G on too fast and too heavy for the limiter to do its job.

 

[BillTIZ]

If a faster speed is needed for safety of flight reasons then that faster speed is permitted by the regulation. No waiver required, applies to civil and military aircraft. DoD has been issued an authorization to operate aircraft at speeds in excess of 250 KIAS below 10,000 feet MSL within active MOAs and MTRs.


How long ago did you leave the game? I spent 30 years in ATC and never saw that in 7110.65.

I left in the early 1980s for a flying career in the AF. I was at ZBOS. It was in Appdx A, but I see the current 7110.65 only have nominal climb / descent rates. The tables used to include airspeeds to expect that to happen.

I kept a copy of 7110.65 on my desk when I was in AF Stan/Eval and on Wing Staff. It's probably been 15 years since I last referenced the Bible.

 

[35 AoA]

I left in the early 1980s for a flying career in the AF. I was at ZBOS. It was in Appdx A, but I see the current 7110.65 only have nominal climb / descent rates. The tables used to include airspeeds to expect that to happen.

I kept a copy of 7110.65 on my desk when I was in AF Stan/Eval and on Wing Staff. It's probably been 15 years since I last referenced the Bible.

Out of curiosity, because I have seen it talked about many times before, what exactly are the duties of the stan/eval guy(s)/gals? As far as I know, we have no counterpart in the USN. I'm assuming you would do check rides. The question being, if that is the case, are we talking tactical upgrade flights (combat section/div lead) or is it an administrative role like doing Instrument and -1 checks (or whatever the AF equivalent of a NATOPS check is called)? Purely wondering here......

 

[Geico266]

And I believe they can do that on a VFR plan as well. I've had a controller tell me to maintain at least 90kts until a certain distance from the airport.

Happens to RV's all the time.

 

[Hank S]

I've been asked to reduce speed for traffic. Flying an ILS with the DPE, a following Lear was told to reduce speed for me; after a brief discussion with him, I came down the GS at 135 indicated instead of 105, to help them out. Still landed with the stall horn squealing. It's all about fitting in.

 

[BillTIZ]

Out of curiosity, because I have seen it talked about many times before, what exactly are the duties of the stan/eval guy(s)/gals? As far as I know, we have no counterpart in the USN. I'm assuming you would do check rides. The question being, if that is the case, are we talking tactical upgrade flights (combat section/div lead) or is it an administrative role like doing Instrument and -1 checks (or whatever the AF equivalent of a NATOPS check is called)? Purely wondering here......

Yes.
I presume your -1 checks are the Equivilent of our Form 8 check rides, due every 18 months when I was on active duty. Tech Order written test, instrument refresher academics, closed book EP test, EP sim and a check flight with all maneuvers, air refuel, low level, sim weapons delivery and instrument approaches.

Check rides have been failed for failure to complete combat tactical maneuvers, threat evasion techniques.

I flew heavies, B-52 and B-1 as a GIB (REO equivilent). I performed Form 8 rides on other GIBs as part of the crew. Flight lead, formation lead qualifications were recommended by Sqd commander, evaluated by Chief of Stan Eval and approved at Group CC level.