Request your best speed
- Thread starter Jhernandez04
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TMetzinger
Final Approach
final approach course?
forward air controller?
I THINK he's referring to the final approach segment.
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kurtsnyder
Pre-takeoff checklist
I don't think there's necessarily a need to come screaming in at 160 or 180kts when given a best forward speed request, unless specifically asked to do so. Keep in mind that many jets, including the 737 normally has an approach speed around 130kts or so.
jspilot
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jspilot
I got the best forward speed request the other day coming back from an xc in a 152. I was going 80kts across the ground flying into a 20 or so knot headwind. I just responded, "this is the best I can do. I'm trying here."ATC came back and said " ok then... Turn right heading 260."Guess it was not good enough!
MarkZ
En-Route
MarkZ
En-Route
Most jets are asked to maintain 160-190 KIAS until the FAF. Beyond the FAF they typically slow to their landing speed, which depends on type aircraft.
One thing forgotten in all this is wake turbulence. ATC cannot deviate from wake turbulence minima. For a small aircraft following a large/heavy/B757, the minima is 6 NM in trail at touchdown. If the small aircraft can fly in the traffic pattern, ATC typically will run an 8 NM in trail final to account for compression inside the FAF.
When you consider that ATC typically provides jets 4 NM in trail spacing down final at 170 knots, the amount of spacing required for a small aircraft adds up rather quickly. On a normal wind day, 4 NM compresses to 3 NM at touchdown (our required separation minima under IFR conditions).
In busy Bravo airspace, a single engine prop that can maintain 120-150 KIAS to a 1-2 mile final can be fit in light traffic. In moderate to heavy traffic, ATC will have to delay a significant amount of jet arrivals to fit the prop in. Which is why sometimes ATC will be unable to accommodate the smaller aircraft.
Palmpilot
Touchdown! Greaser!
Would it help to have the slower aircraft join the procession from a close-in base, so that it doesn't spend as much time on final?
I thought a 152 can do better than 80 KIAS?
He was doing 100kts into a 20kt headwind.
That's what happens VFR to me typically, however that can't be done in IMC.
jspilot
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jspilot
I thought a 152 can do better than 80 KIAS?
You miss read what I wrote. I was indicating about 110 indicated airspeed but my ground speed was 80 knots. Plus it was turbulent so I was not going into the yellow just to please ATC.
I'm pretty sure ATC does not care about indicated airspeed- they just want to know how fast across the ground you are going.
MarkZ
En-Route
I did misread that.
We use indicated speed to get the groundspeed we need. If you let ATC know what indicated speed you're capable of, ATC can figure out how that plays into the general sequence.
My guess is your 110 knots couldn't cut it for what the controller was trying to do. No big deal, you get a turn for a few miles to go into another gap.
spiderweb
Final Approach
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Ben
Yes that's what I meant. But sometimes when I fly it, if I can't center the needle, I shout, "Oh FAC!"
JordanDelaney
Pre-Flight
This happened to me just once while doing an ils approach... approach wanted 130 knots (basically max forward for the 172) to the FAF (which wasn't really possible, since we were at full power while level and waiting for GS intercept). Told approach we were pedaling as hard as we could and we'd do our best 
spiderweb
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Ben
This happened to me just once while doing an ils approach... approach wanted 130 knots (basically max forward for the 172) to the FAF (which wasn't really possible, since we were at full power while level and waiting for GS intercept). Told approach we were pedaling as hard as we could and we'd do our best
If you like Cessnas and want to practice this, go rent a 182 or 210 and fly approaches in a Class C or B. You'll get it frequently.
Captain
Final Approach
??
ATC knows how fast over the ground you are going. If they assign you a speed it's indicated they're talking about. Truth be told, they don't really care about ground speed or indicated speed. They care about relative speed...how fast or slow you are going compared to everyone else. An instruction of 'best forward' speed is just an attempt to get you to flow better with the other aircraft. They know a bigger window will be needed to accommodate you but by going as fast as possible reduces (greatly) the size of the bigger window required.
gismo
Touchdown! Greaser!
You're thinking in 2D. In an airplane, addition to forward speed there's vertical speed.
jspilot
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jspilot
You worded it better than I did but that's essentially what I meant. I was indicating about 110 or so knots but that number is relatively meaningless to the controller because I was actually moving much slower. I would say that they care how fast you are actually moving way more than what the airspeed indicator says you are capable of going in that power setting.
Dr. O
Pattern Altitude
Landed at Cleveland KCLE a couple of years back. Landing fee was $70. Likely, more now.
MarkZ
En-Route
ATC uses indicated speed as the method of maintaining spacing when sequencing aircraft. Letting ATC know you can maintain 110 knots until a certain point on final helps the controller determine the in trail requirement when spacing differing aircraft types.