When to Slow on Approach

[germb747]

Typically I fly into military airfields where you're the only traffic coming in, but the other day I was coming in to Honolulu (PHNL). ATC tends to keep you high and then slam-dunks you in. Well, I saw this coming about 20 miles out when we were at 8,000 feet. So I began slowing to the speed where I can put the flaps to 40% (can't use spoilers in-flight in the C-5) so I could lose energy and begin configuring. There are no speeds posted on the STAR and ATC didn't assign us a speed, but another pilot on the crew commented that at civilian airports, I mess up the whole flow/sequence when I do that.

So, the question is, when do you expect us to slow from 250 KIAS in the absence of a speed restriction? "Cleared for the approach" seems too late in the game, unless you want to see a tactical arrival--I can do that too. If you could point to a publication reference, I'd be happy to review it.

 

[///AMG]

Not a controller, but in my much lighter jet we slow from 250 7-ish nm prior to FAF, dirty around 5 and are on-speed (130ish) by 3 prior. That said, I have normally gotten pilot's descretion on descent anywhere from 40-80 nm out on the road, and we really only do penetrations when we ask for them. I too would be interested to hear the official answer to this question

 

[ian]

Not a controller, but in my much lighter jet we slow from 250 7-ish nm prior to FAF, dirty around 5 and are on-speed (130ish) by 3 prior. That said, I have normally gotten pilot's descretion on descent anywhere from 40-80 nm out on the road, and we really only do penetrations when we ask for them. I too would be interested to hear the official answer to this question

we do the same, except we are at 200-220 instead of 250.

 

[///AMG]

Also, if on vectors to final portion of an approach, we normally slow w/n 30 radials (or degrees depending on type of approach) and 10 NM. I configure on base leg, and get on speed during the dogleg turn generally. That way when we hit the GS or FAF all there is to do is crack the boards out and pull a little power off the jet. I assume you probably have a lot more lift/drag generating devices on your C-5 so I could imagine the process being a bit more complex (we just have a single set of flaps, slats and speedbrakes). If I'm somewhere a little busier and they ask us to maintain best forward speed, I'll just stay at 250 until about 5 prior and then go idle, boards and configure.

As a side note, while chatting with an IP recently, he said he did the same 7-5-3 rule in the Hornet as well. He said that it is actually in FAR/AIM, though I haven't personally seen it.

 

[C150J]

From a 121 pilot's perspective:

Considering that you were high, it sounds like you did everything correctly. Losing roughly 8,000 for a straight-in approach would require roughly 24 miles for a 3-degree slope, so you're going to need to bleed off your speed at some point early on. It makes no sense to intercept the glideslope at its published altitude just to salvage an excessively fast, borderline unstabilized approach. There are PLENTY of civilian terminal areas that do the "slam-dunk," GSO, BTV, IND, and ORF downwinds just to name a few.

Now, if you're below a ~3-degree slope straight-in, depending the airplane, you can generally go 250 to the marker. Who was this other crewmember? Did they realize that you were being held high? Not being able to use spoilers, I don't see the validity in his comment unless he was expecting you to drop the gear out of sequence on a 3 mile final with your hair on fire.

 

[Beehive]

In IMC and heavy traffic VMC I expect 180-190 from 15 miles to the FAF.
Gotta enjoy the Southwest's and GA's who once cleared for an approach 30 miles out slow it to 160. That's got "go around" written all over it.
If you need a speed, let it be known early (50 miles out).

 

[///AMG]

Gotta enjoy the Southwest's and GA's who once cleared for an approach 30 miles out slow it to 160. That's got "go around" written all over it.

I guess it's one thing if you can actually fly clean at 160 kts, but otherwise that is just wasting a ton of gas, and (especially for GA types) burning a big hole in one's pocket.

 

[Beehive]

I guess it's one thing if you can actually fly clean at 160 kts, but otherwise that is just wasting a ton of gas, and (especially for GA types) burning a big hole in one's pocket.

If nobody's in my airspace, i'll let you fly PD's speed all route long.
If i'm controlling a bank: I'm puting a speed on you regardless of company or type. If you can't achieve the speed in a timely manner, it's hold or go-around time.
Analogy- It's like the fat kid holding everybody up at the drinking fountain after running a mile.

P.S. I don't care what it cost any airline or airplane to operate, my job is to separate airplanes. If I don't do that it cost my family.

"If the milk is sour, I'm not the type of • to drink it." -Lock, Stock and Two Smoking Barrels
Great movie.

 

[///AMG]

If nobody's in my airspace, i'll let you fly PD's speed all route long.
If i'm controlling a bank: I'm puting a speed on you regardless of company or type. If you can't achieve the speed in a timely manner, it's hold or go-around time.
Analogy- It's like the fat kid holding everybody up at the drinking fountain after running a mile.

P.S. I don't care what it cost any airline or airplane to operate, my job is to separate airplanes. If I don't do that it cost my family.

Not sure if you are referring to someone wanting to slow down too soon here, but I was speaking to those who want to wait as long as possible to slow for fuel conservation. Do you have a problem with that as long as we are dirty/configured by the FAF and don't violate applicable speed limitations? I know a couple times we had a controller restrict us to 170 kts, which is a very uncomfortable and potentially dangerous speed to cruise around in clean in my aircraft (and conversely too fast for dirty configuration). Is there a better response to this than "unable"?

 

[Baronman]

I know a couple times we had a controller restrict us to 170 kts, which is a very uncomfortable and potentially dangerous speed to cruise around in clean in my aircraft (and conversely too fast for dirty configuration). Is there a better response to this than "unable"?

What are you flying? What's so "uncomfortable" about 170 kts? How can it be potentially dangerous yet too fast for some flaps or slats? Seems odd that there's a speed that you have to avoid.

 

[///AMG]

What are you flying? What's so "uncomfortable" about 170 kts? How can it be potentially dangerous yet too fast for some flaps or slats? Seems odd that there's a speed that you have to avoid.

T-45C Goshawk; it is perhaps a slightly unusual player, but I wouldn't be surprised if there were other high performance jets in the same boat. Depending on fuel load, 170 kts clean doesn't leave much margin for error in any sort of turn (our little swept wings don't like to loose the lifties at that speed), not to mention our wheels warning horn intermittantly sounding off (annoying). Any slower and we are getting on the backside of the power curve and close to stall. In the dirty configuration we are burning damn near 3 times as much gas as we normally would be in a nice 200-250 kt clean cruise. We can make it happen, but it is uncomfortable in any configuration in level flight. Hope that explains what I was talking about.

 

[MikeD]

What are you flying? What's so "uncomfortable" about 170 kts? How can it be potentially dangerous yet too fast for some flaps or slats? Seems odd that there's a speed that you have to avoid.

LOL. In the F-117, anything below 250 clean was uncomfortable. 300+ was normal penetration. Didn't help that there were no flaps or slats at all, or any other drag device other than the landing gear and the drag chute.

There are many highly swept-wing planes that don't like playing slow, since they almost have no wing in a manner of speaking.

 

[fish314]

T-45C Goshawk; it is perhaps a slightly unusual player, but I wouldn't be surprised if there were other high performance jets in the same boat. Depending on fuel load, 170 kts clean doesn't leave much margin for error in any sort of turn (our little swept wings don't like to loose the lifties at that speed), not to mention our wheels warning horn intermittantly sounding off (annoying). Any slower and we are getting on the backside of the power curve and close to stall. In the dirty configuration we are burning damn near 3 times as much gas as we normally would be in a nice 200-250 kt clean cruise. We can make it happen, but it is uncomfortable in any configuration in level flight. Hope that explains what I was talking about.

Hey AMG, what is the max Flap speed in the Goshawk, and what's the approach speed with the flaps?

 

[Hacker15e]

I don't think that he was looking for other military dudes to answer his question!

 

[Baronman]

Ok..Sure it makes sense for a military plane. I wouldn't imagine your find yourself in 30 minute sequences for airports where it be a real pain in the butt.

 

[///AMG]

Hey AMG, what is the max Flap speed in the Goshawk, and what's the approach speed with the flaps?

Flaps/slats max is 200, though technically speaking the design limit is 217. We don't have an approach speed per se, but we fly the equivalent airspeed for a constant 17 units AoA for a given configuration as on speed. On speed with half flaps is 131 + 1/2 fuel load (ie at 2000 lbs of gas, approach speed is 141 kts). Full flaps is 111 + 1/2 fuel. Normally our practice approaches are shot half flap, but we full stop with full flaps, which normally has us in the 115-120 kt range. For reference though, on speed no flap/slat is 151 + 1/2 fuel, so you can see where clean at 170 with a big fuel load is not ideal.

Hacker, I too am interested in hearing a civilian controller's response

 

[Beehive]

Not sure if you are referring to someone wanting to slow down too soon here, but I was speaking to those who want to wait as long as possible to slow for fuel conservation. Do you have a problem with that as long as we are dirty/configured by the FAF and don't violate applicable speed limitations? I know a couple times we had a controller restrict us to 170 kts, which is a very uncomfortable and potentially dangerous speed to cruise around in clean in my aircraft (and conversely too fast for dirty configuration). Is there a better response to this than "unable"?

I like your style here and i'm all for it. Just get the preceeding aircraft in site and i'm good to go.
During arrival banks, i'm slowing everybody to 190kts to 170kts. If unable at any larger airport, I advise you have the center let approach know.

 

[N519AT]

There are many highly swept-wing planes that don't like playing slow, since they almost have no wing in a manner of speaking.

Like the T-38? The wing looks ridiculously small for an aircraft of it's size.

 

[Hacker15e]

Like the T-38? The wing looks ridiculously small for an aircraft of it's size.

Hence the airplane's 300-knot "min safe airspeed" and the airspeed waiver below 10K.

 

[TUCKnTRUCK]

I like your style here and i'm all for it. Just get the preceeding aircraft in site and i'm good to go.
During arrival banks, i'm slowing everybody to 190kts to 170kts. If unable at any larger airport, I advise you have the center let approach know.

For a short while, we had to configure (I.e, drop gear) below 180kts... Below 180 clean in a Q gets a little uppity. It will do it, but your deck angle gets pretty high, and she gets sloppy. You get pretty close to the back side of the power curve.