CDreier
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Question About Approach Speeds.

Fri Nov 16, 2012 9:05 pm

This is a question about approach and landing speeds at large terminal airports. Using a B763 as an example, suppose the Vref is 135 knots on a lightly loaded aircraft. Would an aircraft flying an ILS be expected to be at the 135 knots+xx at the final approach fix and descend the entire flight path at Vref, or would it cross at some higher speed and bleed off speed to Vref when closer to the runway? Since each aircraft has its own Vref that can vary by many knots it would seem speed could create many conflicts on an instrument approach. Yes, I know controllers will often ask for a certain speed to the marker, etc.. But what about those times when it's up to the flight crew? What is a good or standard practice? Thanks.

[Edited 2012-11-16 13:11:26]
 
Mir
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RE: Question About Approach Speeds.

Fri Nov 16, 2012 9:54 pm

General practice is to be established on approach speed (which might be Vref, or might be Vref + some correction factor) by 1000' AGL in instrument conditions and 500' AGL in visual conditions in order to meet stabilized approach criteria.

Quoting CDreier (Thread starter):
Since each aircraft has its own Vref that can vary by many knots it would seem speed could create many conflicts on an instrument approach.

That's what ATC is there for - to ensure that spacing remains adequate. And they're pretty good at it.

-Mir
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CDreier
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RE: Question About Approach Speeds.

Fri Nov 16, 2012 10:05 pm

Does that imply a standard or predetermined speed coming down the glide slope? I know approach charts indicate times to MAPs based on speeds such as 160 knots.
 
Mir
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RE: Question About Approach Speeds.

Fri Nov 16, 2012 11:28 pm

Quoting CDreier (Reply 2):
Does that imply a standard or predetermined speed coming down the glide slope?

Unless something is specified, either by ATC or by the chart, no.

Quoting CDreier (Reply 2):
I know approach charts indicate times to MAPs based on speeds such as 160 knots.

If I was going to be using timing to determine my MAP (but with modern avionics there's really no need to for most approaches), then I would want to be flying my approach speed the whole way from the FAF in. But that doesn't apply to the portion of the approach outside the FAF, and like I said it doesn't happen very often.

-Mir
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vikkyvik
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RE: Question About Approach Speeds.

Sat Nov 17, 2012 12:01 am

Quoting Mir (Reply 1):
General practice is to be established on approach speed (which might be Vref, or might be Vref + some correction factor) by 1000' AGL in instrument conditions and 500' AGL in visual conditions in order to meet stabilized approach criteria.

And as far as I know, airlines may specify different procedures, like 1000' in all conditions or whatever.

Not sure if there are minimum criteria specified in the FARs or anything. I would tend to doubt it.
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Mir
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RE: Question About Approach Speeds.

Sat Nov 17, 2012 1:41 am

Quoting vikkyvik (Reply 4):
And as far as I know, airlines may specify different procedures, like 1000' in all conditions or whatever.

They may. And they may also specify certain speeds to be flown at certain points on the approach absent other instructions from ATC, but I can't comment on any of those.

-Mir
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tdscanuck
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RE: Question About Approach Speeds.

Sat Nov 17, 2012 1:59 am

Quoting CDreier (Thread starter):
Would an aircraft flying an ILS be expected to be at the 135 knots+xx at the final approach fix and descend the entire flight path at Vref, or would it cross at some higher speed and bleed off speed to Vref when closer to the runway?

In the example of a 767, you'd expect it to be at Vref+5+1/2 the gust at the time the airline's procedures require them to be on a stabilized approach. This may or may not be the FAF. It would be very unusual to have an aircraft cross the FAF or the threshold at Vref.

Quoting CDreier (Thread starter):
Since each aircraft has its own Vref that can vary by many knots it would seem speed could create many conflicts on an instrument approach

This only becomes and issue if you're operating at minimum spacing and, for airports with that issue, ATC is very very good at managing this. ATC cannot dictate approach speeds (they can request them) because they don't know the weight of the aircraft.

Quoting CDreier (Thread starter):
But what about those times when it's up to the flight crew?

It's always up to the flight crew.

Tom.
 
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zeke
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RE: Question About Approach Speeds.

Sat Nov 17, 2012 2:31 am

Quoting CDreier (Thread starter):
Using a B763 as an example, suppose the Vref is 135 knots on a lightly loaded aircraft.

The category the aircraft is filed under is normally at their maximum weights, not actual weights.

Quoting CDreier (Thread starter):
Would an aircraft flying an ILS be expected to be at the 135 knots+xx at the final approach fix and descend the entire flight path at Vref, or would it cross at some higher speed and bleed off speed to Vref when closer to the runway?

The expectation for a Cat C aircraft (threshold speed between 121-140 kts), the range of speed from the initial approach fix is 160-240 kts, and final approach speeds (115-160 kts). A lot of airports I fly into expect me to maintain 160 kts until 4 nm, so it would not be unusual to be at the reference speed not until around 1000 ft, or at least decelerating towards it. We actually operate all of out aircraft to Cat D standards, which allows for higher speeds again, the downside is the minima maybe higher.

Quoting CDreier (Thread starter):
But what about those times when it's up to the flight crew? What is a good or standard practice? Thanks.

Still try and keep the aircraft clean as long as possible, even without ATC constraints. I would not normally select landing flap until approaching 1700/1600 ft, allowing time for the landing checklist to be completed by 1500 ft. Decelerating to approach speed once final flap is selected. A bit of experience needs to be used, often ATC will throw in a radio call there somewhere, they crew still has to fly/configure the aircraft.

Quoting Mir (Reply 5):
And they may also specify certain speeds to be flown at certain points on the approach absent other instructions from ATC, but I can't comment on any of those.

Our criteria is 1000 ft regardless of the IMC/VMC, however the speed is not hard, we have to be at a sensible speed for the conditions. This means possibly decelerating to approach speed after maintaining 160 to 4, or a typhoon with wind in excess of 50 kts at 1000 ft. The other hard speed we maintain is min clean/250 below the MSA.
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Fabo
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RE: Question About Approach Speeds.

Sat Nov 17, 2012 10:54 am

Very basic rule of thumb that seems to work out rather well normally is ~180 for localizer capture, then slow down to 160, fly that until 4-5 miles out, then slow down.

Keep in mind that some aircraft are better at slowing down than others, then it also depends on current weight and landing flap config. The crew will usually be aware though, and can notify the ATC in advance if they are unable to slow down in allocated space, even when using all available methods.
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speedbird128
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RE: Question About Approach Speeds.

Mon Nov 19, 2012 2:15 am

Quoting tdscanuck (Reply 6):
It's always up to the flight crew.

Inside of 4 or 5nm final, yes. Outside of that its my speeds or my headings. And I can see who lies to me.

We are also trained to expect varying approach speeds, like a heavy 747 on landing will eat up a light B737 on the approach.
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LONGisland89
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RE: Question About Approach Speeds.

Mon Nov 19, 2012 2:46 am

Quoting speedbird128 (Reply 9):
And I can see who lies to me.

I think that is awesome. I saw in another thread that you can see IAS and MCP alt. Can you explain how the technology works? We don't see that at all over here in the U.S.
 
PGNCS
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RE: Question About Approach Speeds.

Mon Nov 19, 2012 3:56 am

Quoting speedbird128 (Reply 9):
Inside of 4 or 5nm final, yes. Outside of that its my speeds or my headings. And I can see who lies to me.

And I can always say unable.
 
BigSaabowski
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RE: Question About Approach Speeds.

Mon Nov 19, 2012 4:44 am

Realistically, at any half-way busy airport, you will be assigned speeds during most of the approach. The last speed assignment you typically get is requested to be maintained until final approach fix (i.e. "maintain 170 knots until ABCDE, cleared for the ILS approach runway 36"). The most common speed assignments given within 15 miles of the airport are in the range of 160-210 knots. Passing the final approach fix is when you usually slow to your Vref plus factor and you will never be assigned a speed after the final approach fix.
After the final approach fix, the ΔVref between consecutive aircraft is almost never more than 15 knots so you will rarely have conflicts because of that.
 
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CARST
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RE: Question About Approach Speeds.

Mon Nov 19, 2012 9:05 am

Quoting LONGisland89 (Reply 10):
I think that is awesome. I saw in another thread that you can see IAS and MCP alt. Can you explain how the technology works? We don't see that at all over here in the U.S.

Very technical, but you can get most information from this Wiki page:
http://en.wikipedia.org/wiki/Air_tra..._radar_beacon_system#Radar_display

And you might want to read this:
http://en.wikipedia.org/wiki/Transponder_%28aviation%29
 
speedbird128
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RE: Question About Approach Speeds.

Mon Nov 19, 2012 4:00 pm

Quoting PGNCS (Reply 11):
And I can always say unable.

Most definitely, you are 100% correct, and I will never assign impossible speeds either.

But I detest the non-compliance which screws my sequencing.
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speedbird128
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RE: Question About Approach Speeds.

Mon Nov 19, 2012 8:52 pm

Quoting LONGisland89 (Reply 10):
I think that is awesome. I saw in another thread that you can see IAS and MCP alt. Can you explain how the technology works? We don't see that at all over here in the U.S.

Please see the other thread, I have posted a picture of my normal data block with explanations...
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LONGisland89
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RE: Question About Approach Speeds.

Tue Nov 20, 2012 3:22 am

Quoting CARST (Reply 13):

I was specifically asking about being able to see MCP alt and IAS. I am very familiar with transponders  
 
tdscanuck
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RE: Question About Approach Speeds.

Tue Nov 20, 2012 4:11 am

Quoting LONGisland89 (Reply 16):
I was specifically asking about being able to see MCP alt and IAS.

It's part of the ADS-B data coming down over the Mode-S extended squitter (aka 1090ES). Not all aircraft do this today...eventually, they all will, if NexGen/SESAR ever get their act together.

Tom.
 
Max Q
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RE: Question About Approach Speeds.

Tue Nov 20, 2012 7:00 am

Quoting tdscanuck (Reply 6):

In the example of a 767, you'd expect it to be at Vref+5+1/2 the gust at the time the airline's procedures require them to be on a stabilized approach. This may or may not be the FAF. It would be very unusual to have an aircraft cross the FAF or the threshold at Vref.

That's not our procedure. We fly VREF + half the steady reported headwind and all the gust (up to 20 knots above VREF)
if the reported wind is less than 10 knots we just add 5 to the VREF.


As an example if the wind is reported as a steady 16 knots you would add 8 knots to VREF.


If it was reported as 16 knots gusting to 26 knots you would add 18 knots (half the steady 16 knots and all of the 10 knot gust) to VREF.
The best contribution to safety is a competent Pilot.
 
tdscanuck
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RE: Question About Approach Speeds.

Tue Nov 20, 2012 1:57 pm

Quoting Max Q (Reply 18):
That's not our procedure. We fly VREF + half the steady reported headwind and all the gust (up to 20 knots above VREF)
if the reported wind is less than 10 knots we just add 5 to the VREF.

You're absolutely right. I had a complete brain fart there.

Tom.
 
Max Q
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RE: Question About Approach Speeds.

Wed Nov 21, 2012 5:23 am

Quoting tdscanuck (Reply 19):

Reply 19, posted Tue Nov 20 2012 08:57:28 your local time (15 hours 25 minutes 25 secs ago) and read 27 times:

Quoting Max Q (Reply 18):
That's not our procedure. We fly VREF + half the steady reported headwind and all the gust (up to 20 knots above VREF)
if the reported wind is less than 10 knots we just add 5 to the VREF.

You're absolutely right. I had a complete brain fart there.

I'm very familiar with my own !
The best contribution to safety is a competent Pilot.

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