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Pilots, 250 Below 10  
User currently offlinePW4084 From United States of America, joined Mar 2001, 291 posts, RR: 0
Posted (12 years 6 months 4 weeks 1 day 18 hours ago) and read 2967 times:

Ok guys this is a bit of an informal poll for those of you flying jets and anything else that needs to slow to 250 KIAS before leaving 10,000 on yr descents. My question doesn't apply to VNAV of FMS descents that do the calculating for you, I want to know what yr techniques or procedures are for making that speed restriction.
I've been in the habit of cutting my VVI to about -1000 FPM at around 12,000... and in the airplanes I fly, throttles at forward idle will slow me from my enroute descent speed of 310 to 250 right before I reach 10,000 feet. Of course I might have to make an adjustment to that and maybe even level off for a few seconds to burn off the last 10 knots or so if I got behind for some reason.
Would you descend all the way to 10, level off and slow to 250 and then resume yr descent?? I recognize that maybe some really clean airplanes (757 maybe) can't slow and descend much at all without full speed brakes so I'm curious how different people approach this.


10 replies: All unread, jump to last
User currently offlineB747skipper From , joined Dec 1969, posts, RR:
Reply 1, posted (12 years 6 months 4 weeks 1 day 17 hours ago) and read 2946 times:

This is both flying techniques and legality question...
Many countries outside the USA do not abide by a 250 below 10 rule, and if there is a note that specifies a speed reduction ATC controllers can waive it, except in USA... In many countries there is a SLP speed limit point published, not always at 10,000 feet or FL 100... We can ask the controller for higher speed if traffic permits. What I personally do with a 747, is to be at 250 speed exactly 30 NM from touch down point...
As far as slowing down technique (sometimes descending barber pole, or an economical 280 as a speed), I like a progressive reduction down to 250, and this without level off, unless otherwise cleared... Maybe it is more confortable to the passengers to be progressive in the speed reduction.
The 747 is not easy to slow down, extremely clean aerodynamically... to give you an idea, if you are at 350, level flight, and want to slow it to 250, it takes all the engines at full idle, and 10 NM distance, to reduce down to 250...
I do not like speed brakes, they rumble the cabin... "oh my God we are going to crash" is not the comment I like to hear being said by the passengers... and further, for fuel economy, I like to stay "clean configuration" as long as it is possible, maneuvering sometimes at Vref + 80 still clean... For me, flaps are there as source of additional lift, not as brakes...
And of course, throw all these rules by the window, when you have a check ride with your check pilot. Then, it is "whatever it takes" and "speed limits" with speed brakes and/or flaps... if not the gear itself...
Happy contrails  Smile
(s) Skipper

User currently offlineJetguy From , joined Dec 1969, posts, RR:
Reply 2, posted (12 years 6 months 4 weeks 1 day 17 hours ago) and read 2921 times:

The technique that I learned back when I was flying for an airline was:
Top Of Descent (TOD) = 3 times desired altitude loss = Descent Point
Rate of descent = 6 times the ground speed.

This works well for every jet I've flown.

It's a formula that I don't use very often any more. The FMS has a VNAV computer that calculates it for you and displays it on the EADI.


User currently offlineCx flyboy From Hong Kong, joined Dec 1999, 6811 posts, RR: 55
Reply 3, posted (12 years 6 months 4 weeks 17 hours ago) and read 2774 times:

If I am in FlightLevel Change, and need to manually reduce from our usual descent speed of 300kts to 250kts, I will wind the speed back to 250 around 2000ft before the applicable altitude. The aircraft will pitch up and maintain idle thrust until 250kts. If I am in VNAV, it will do it automatically.

User currently offlineMandala499 From Indonesia, joined Aug 2001, 7561 posts, RR: 76
Reply 4, posted (12 years 6 months 4 weeks 7 hours ago) and read 2697 times:

How about "request high speed below 10" Big grin


When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlinePW4084 From United States of America, joined Mar 2001, 291 posts, RR: 0
Reply 5, posted (12 years 6 months 4 weeks 5 hours ago) and read 2677 times:

Yeah, I like that answer also Mandala499.

I appreciate yr responses guys, nice to hear different twists on something so routine.

Just out of curiosity Skipper, Do you typically begin yr descent at basically cruise mach (.84, .82, whatever) and then catch yr desired KIAS (320, 300, whatever) when they meet?

thanks again, PW4084

User currently offlineB747skipper From , joined Dec 1969, posts, RR:
Reply 6, posted (12 years 6 months 3 weeks 6 days 22 hours ago) and read 2631 times:

Dear PW4084 -
Exactly like you said for the descent... in the 747...
We use the existing cruise Mach number, could be as high as .86, but generally at end of cruise we slow down to about .825 or .83, then we use either a high speed descent at 320, a normal descent 300, or economy 280 KIAS...
Happy contrails  Smile
(s) Skipper

User currently offlineWing From Turkey, joined Oct 2000, 1601 posts, RR: 23
Reply 7, posted (12 years 6 months 3 weeks 6 days 9 hours ago) and read 2550 times:

We mostly use econ speed for the cruise which is .78/.79 in B737800.And it gives you a 280 kts during econ descent.Unless otherwise instructed to reduce 250 from 280 I use LVL CHG mode.1000 feet before the desired altitude.VS mode is only used for descents less than 2000feet(ex:from 25000 to 24000)because if you use the LVL CHG thrust levers comes to idle and aircraft pitches down to keep the speed dialed on speed window at MCP.This is not a comfortable thing for the passengers who doesn't like the roller costers too much.Another way to use the VS mode when you don't have too much traffic around you and you are cleared for a high speed approach you can plan according to your descent rate not bother about the speed(since you can't descent with 2000fpm and reduce speed at the same time)What we can do with it this case you can either descent with a less VS and keep the speed in control(aproximetely)or descent with higher rate few miles infront of desired point and reduce speed in straight and level flight(737 looses 10 kts in 1 NM in straight and level flight)

In busy terminal areas its more important to have a speed control since there are traffics behind and infront of you preferred method is to use the LVL CHG unless a certain rate dictated by ATC.And also in some terminal areas (like some German airports for example)there are SLP's you have to be at certain speed not at FL100 but at a certain point.So if you use VS Mode we may not be able to be at the speed we want at given point since we have not much control on the airspeed.

I also want to add something about the use of speed brakes.Unless dictated by ATC,or required by some other reason if as pilot has to use speed brks with his own descent means that he made a poor descent planning.I agree with captain 747skipper most passengers are scared with the sound of the speed brakes.But in anyways if I have to use it I never hesitate to use it.Its better than lowering gears early or trying to extend downwind in a busy area.

follow me on my facebook page" captain wing's journey log"
User currently offlineBa299 From United Kingdom, joined Jun 2003, 173 posts, RR: 1
Reply 8, posted (12 years 6 months 3 weeks 6 days 6 hours ago) and read 2531 times:

With the 777 in BA it depend by the type of engine that the aircraft have. With the GE engine normally we descend with the VNAV mode so it command flight idle and 300kt till FL100 and 250kt below FL100 all automatically.
With the RR engine normally we descend with flightlevel change we to manually the work of the FMC and we select 250kt about 2000ft above FL100.
If we are lucky we and we don't have seep limit by ATC we descend with 300kt also below FL100.

User currently offlineB747skipper From , joined Dec 1969, posts, RR:
Reply 9, posted (12 years 6 months 3 weeks 5 days 21 hours ago) and read 2474 times:

Use of speed brakes...
ATC - < ABC123, expedite descent to 2,000 feet, reduce speed to 200 knots.
Pilot - < Approach, unable to comply, do you want altitude or speed first...?
ATC - < ABC123, suggest you use your speed brakes...
Pilot - < Approach, speed brakes are for MY mistakes, not YOUR poor planning...
Happy contrails  Smile
(s) Skipper

User currently offlineMandala499 From Indonesia, joined Aug 2001, 7561 posts, RR: 76
Reply 10, posted (12 years 6 months 3 weeks 4 days 23 hours ago) and read 2396 times:

Slightly off topic here, but I thought I'd share this with you:

2 Extremes

1. LH778:
LH: Jakarta Arrivals, LH778 with you passing 330 for 10,000 direct DKI"
ARV: 778, Guten tag, you have traffic ahead 4 737s approaching DKI for downwind, if you want, I can give you heading 220 maximum speed and maybe about 5000 fpm descent to put you ahead of them. Do you want to take it?
LH: Arrivals, standby... 778... (voice in background goes "Ja we take it!) Arrivals, 778 will take that...
ARV: OK, 778, turn to 220, descend to 6000 max speed and max descent, cancel speed below 10, transition level is 120 call reaching 6000.
LH: 778 passing 310 now will call reaching 6000.

6 minutes later.
LH: Arrivals, Lufthansa 778 approaching 6000... you want us to slow down?
ARV: Yes please, reduce to 220knots, turn heading 250 call approach 12545.

2. KLM 837
ARV: KLM837 call approach 12545...
KL: 12545, KLM 837... Approach, KLM 837 with you passing 120 for 6000.
APR: KLM837, turn to 250 for downwind, descend to 4000, cancel speed below 10.
KL: Errr, 837 would like to self restrict to 250 below 10 please.
APR: Negative 837, you have many traffic coming behind you FAST.

An MH 777 pilot and former 734 pilot told me before that Jakarta ATC likes planes to come in high and fast... now I know what they meant...


When losing situational awareness, pray Cumulus Granitus isn't nearby !
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