Maintain speed until.......

Cruise

Cruise

Well-Known Member
Ok, I've been curious about this one........and I should remember the answer to it.....but, my brain is melting from all the upgrade studying....so I don't. :confused:



When the controller asks a fight to maintain a particular speed until an xyz final.....what is being used to determine the final distance? Threshold? Obviously if it's an ILS DME, then it would stand to reason you'd use the DME measurement......however, what happens when the DME used for the approach isn't co-located w/ the ILS?


For example: ILS 19R into KIAD

DME is predicated off of ARMEL VOR which is easily 1/4 - 1/2 mile south of the far end of the runway. 19R is 11,500 ft. long, so it's nearly three miles from the VOR to the threshold of 19R. Now, if asked to maintain 180kts. until a 5 mile final, is this distance being determined from the DME readout (basically 2 miles to the threshold) or would it actually be 8 DME (5 miles from the threshold)?

Does this make sense? Or am I hopelessly :insane:?


KIAD ILS 19R
 
This is a good question. If a controller offers a clearance like "maintain 150 knots until 5 miles", he or she usually means 5 miles from the touchdown point. You are more apt to hear a controller ask you to keep an assigned speed to a definable fix "maintain 170 to the marker" or "maintain 190 until FRISH." Be careful not to allow ATC to fly your airplane for you. If you can accommodate their desires safely - great. If not, fly at safe speeds and let ATC sort out the problem.
 
calcapt said:
This is a good question. If a controller offers a clearance like "maintain 150 knots until 5 miles", he or she usually means 5 miles from the touchdown point. You are more apt to hear a controller ask you to keep an assigned speed to a definable fix "maintain 170 to the marker" or "maintain 190 until FRISH." Be careful not to allow ATC to fly your airplane for you. If you can accommodate their desires safely - great. If not, fly at safe speeds and let ATC sort out the problem.
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Thanks for the response CC......and I definitely agree about being more likely to hear about the "definable fix" because it certainly removes all doubt this way. Nevertheless, I had this very thing happen (maintain speed until 5 miles) today. IMO, I also agree with you, that when asked to maintain speed until a certain final distance it should be relative to the TDZ or threshold......but I was curious if there is an actual "correct/incorrect" answer.

Also, you make a great point that it's great to help ATC out, but a person (crew) should first fly the plane safely, and let ATC work out the logistics if it's not meshing with the traffic flow.
 
Typically these maintain speed clearances are to keep you from slowing down and slowing up the line behind you. After you have satisfied the request of the controller, it is assumed that you can now configure and slow the aircraft to your normal approach speed which is generally slower than what you had been assigned by ATC. Since you will NEVER slow to below your approach speed, why would you want to increase speed? But to answer your question: Once you have satisfied the clearance issued, you can fly whatever speed you want until ATC calls you again and asks WTF?
 
mikecweb said:
Here's my question:
They tell you to maintain 150 to the marker....can you speed up after that?
Click to expand...

I'm not ATC; but my thoughts on this would be NO.

Unless you're flying something "uberheavy," you're probably going to be configured and slowing below 150 after the marker, so why would you want to increase speed?

It's a good question though......again, I'm curious how it turns out.
 
Cruise said:
Nevertheless, I had this very thing happen (maintain speed until 5 miles) today.
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They do this all the time in CLT. In fact, it's usually exactly that, maintain 150 kts or greater (or whatever speed), until a 5 mile final. I've always just used the DME off the ILS, and have never had a complaint. In my experience they'll use distance if there's DME on the ILS, if there's no DME then you'll get a fix (til the marker, etc). Pretty much what's been said above. :)
 
If you're told maintain an airpseed until the fix, after you cross the fix you can fly any speed you'd like. As far as maintain until x miles, I'd assume DME since DME distance is more or less the go to distance measurment in ATC. If ATC isn't being too specific it isn't an imminent problem and more of a safeguard. If it is THAT big of a deal, the controller will tell you X miles from the threshold etc. Also, about the maintain X until at Y then faster... Were you in a King Air behind a Cub and in front of an 767? Sounds like some controller might have had some choice words with the guys in approach control for that sequencing.
 
When an air speed is assigned til fix or x # of miles I mean til the rwy appch end. Once you have met that request, speeding up would not be necessary providing that the guy behind you did maintain his assigned air speed and therefore enough spacing was acquired.:bandit:
 
:yeahthat:
I'll fly the Caravan typically 170kts till 300-400ft. AGL.
Baron marker at 170kts, 150kts at 1,00agl 120kts at the bottom.
 
It's really easy to fly a speed to a five mile final with no DME. Just range the MFD down and when the airport appears on the 5 mile ring just start slowing. See, SJS isn't ALL bad.:)
 
jonnyb said:
In a hurry eh?:) Why so fast? Especially in that airplane.
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Would you rather him do 125??? When I flew the van, I kept it as fast as possible to keep me from slowing everybody else down. I always met up with at least 4 of our airplanes and other aircraft inbound. ATC always appreciated it, so I did it safely.

Now I'm trying to get out of the habit:bandit::D.
 
jonnyb said:
In a hurry eh?:) Why so fast? Especially in that airplane.
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Being on time matters to some airlines.:bandit::sarcasm:
Its just seems natural to me at this point. If I shot an approach at 130 or 120 I would fall asleep from it taking to long.
 
Cruise said:
Ok, I've been curious about this one........and I should remember the answer to it.....but, my brain is melting from all the upgrade studying....so I don't. :confused:

When the controller asks a fight to maintain a particular speed until an xyz final.....what is being used to determine the final distance? Threshold? Obviously if it's an ILS DME, then it would stand to reason you'd use the DME measurement......however, what happens when the DME used for the approach isn't co-located w/ the ILS?
Click to expand...


A little modification of that question: If you were issued a speed restriction while on an approach but ATC did NOT specify a fix/distance, at what point are you allowed to slow down? To be more specific: Does the clearance for the Visual Approach automatically cancel the restriction?
 
k4air said:
A little modification of that question: If you were issued a speed restriction while on an approach but ATC did NOT specify a fix/distance, at what point are you allowed to slow down? To be more specific: Does the clearance for the Visual Approach automatically cancel the restriction?
Click to expand...

From AIM 4-4-11.f

Approach clearances supersede any prior speed adjustment assignments, and pilots are expected to make their own speed adjustments, as necessary, to complete the approach. Under certain circumstances, however, it may be necessary for ATC to issue further speed adjustments after approach clearance is issued to maintain separation between successive arrivals. Under such circumstances, previously issued speed adjustments will be restated if that speed is to be maintained or additional speed adjustments are requested.
 
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