What's normal speed for a 737 at 10 miles out on approach?


#1

I ask because I live just over 10 miles from AUS and this flight seemed to be coming in faster than normal. I live close to the normal flight path, so I see many flights a day, some going directly overhead.

flightaware.com/live/flight/SWA2228

Maybe it was just my imagination. The log shows it was going about 248 knots at my location (30.3757N).


#2

248 knots is allowed and happens from time to time, but I wouldn’t say it’s “normal”. Under normal circumstances, aircraft need to be under 250 kts when under 10000 feet - so they can be at that speed as long as they want, assuming ATC allows and it makes sense for the aircraft to approach at that speed. 10 miles is still a long way and a 737 has plenty of time to slow to its approach speed in that distance.


#3

Thanks for the informative reply. So it sounds from your answer that it’s OK but probably faster than normal. That would confirm my impression that this particular plane was going faster than the other planes I see. I don’t think it had flaps down, but I couldn’t really tell. The first thing I noticed was that it sounded different than normal.

For grins I fired up my X-Plane iPad app and loaded up its 737 to see how it behaved under those conditions. I had no trouble getting it to normal speed by ground level with only 1/3 flaps. I do realize that X-Plane is probably not that accurate, but it’s all I have.

EDIT: Wait a minute. Did you mean under 2000 feet instead of 10000 feet? This plane was going almost 400 knots at under 10000 feet.


#4

I just found this:

"91.117 Aircraft Speed

(a) Unless otherwise authorized by the Administator, no person may operate an aircraft below 10,000ft MSL at an indicated airspeed of more than 250 knots.

(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. 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.

© 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.

(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."

So I guess (a) maybe applied in this case (as well as the next SWA plane to pass by, this one from Phoenix rather than El Paos). Obviously, I’m too far out for (b) to apply.


#5

Flightaware gives ground speeds instead of indicated airspeeds, although this difference is certainly very large.


#6

Air speed would be even greater, then, since wind today is coming from the south. That would generally be the case since planes generally land/take off up-wind.


#7

Maybe the controller wanted a particular speed for spacing…or there was no particular need to slow the aircraft up to the outer marker, let him fly. (Signal Buster?)

If you see this again, look to see how far in trail the next aircraft is ( if there is one).


#8

I did pay attention to traffic following that one. I didn’t think it was that close, and it was coming from Houston. I just looked it up, and it arrived 5 minutes later and it used the other runstrip. The same runstrip was not used again for 25 minutes (except maybe for traffic that doesn’t show up on flightaware and that I also don’t see from my location).


#9

Runstrip…I like that!!!

Well, who knows why? Just another day in the Wild World of Aviation…


#10

Here’s the permalink for the flight (It is the ELP-AUS segment on 30 May, right?)
flightaware.com/live/flight/SWA2 … /KELP/KAUS


#11

That’s correct. I notice the flight the next day was even faster according to the flightaware data. By the way, my location is essentially right on the outside of two circles on the sectional map. I assume that indicates the perimeter of the class C airspace, where class E transitions to the 45/21 class C space. Am I reading the sectional correctly? Maybe the pilots are trying to get within the 250 knots by the edge of the class C space rather than when they drop below 10,000 feet?


#12

You’re reading too much into it. At my ATC facility (Chicago TRACON), aircraft typically will do 250 knots till 15 mile final, 210 till 10 out, and 170 or 180 till 5 or so miles out. On a nice VFR day, sometimes they will stay a little faster longer, but the B737 and B738s like to slow a little earlier than some of the older 737’s. I have never seen a groundspeed faster than 240 at the final approach fix before (it was an E135), and never that high on a 737. I have seen 250 groundspeed 10 out though going into MDW, on a nice day when the aircraft was below the glideslope.