More unheard of ideas: NG speed restriction

[Pin Head]

Heard today that the NG is speed restricted to 250kts below 10000ft.

I know that the 756 has a bird strike protection airspeed limitation but the NG?

I just like to energy manage so it would be nice to know as I have regularly flown high speed unless there is a bird race going on.

[Capn Bloggs]

Windup alert!

[megan]

Think Pin Head is a rather apt name.

[Lucky8888]

You've got that right.

[underfire]

ummmm...AFAIK it is well understood that the NG, albeit ALL B models, have a speed restriction of 240 kts below 10K coded in to the system, so the drivers dont blow the check ride. (tailwind?)

[Capn Bloggs]

Only in America... :rolleyes:

[underfire]

sorry Bloggs, I think it is a B thing...it was like that on the QF variants...

When doing the coded procedures, set a waypoint at 10K with a speed restriction of 250, that way, (or coming off the STAR) the box would use it for TOD and a continuous descent..AB variants worked fine with this, but the B variants would disco...

[RAT 5]

There are multitude of reasons 250/100. Regarding the default 240/100 (B767) I was alway told it was an FAA thing to allow a 10kts overspeed and not bust their ATC limits????

Curious: I flew for one operator (B737) who was on a fuel saving spree. The CI chosen gave 245kts in descent after mach changeover. They still manually entered 250/100. How daft was that??!?

[Capn Bloggs]

The Vmo of the 737NG "here" below 10k is 340, as it is with my "little Boeing".

[Huck]

Hope you don't hit a bird....

[LeadSled]

Hope you don't hit a bird....

Huck,
Speaking from experience, there is little difference between hitting a bird at 250KT and 350KT. Fortunately, in my case, neither were Canada Geese.
Tootle pip!!
PS: The actual history of bird strikes (or in the case of TAA, a snake) at high IAS/TAS and high (ish) altitude makes interesting reading.

[de facto]

Pin head.
You really are a crack up.
Sometimes you have legit questions and sometimes your posts,such as this one just makes me wonder.

If you reach 251 kts on the NG,all spoilers(including ground spoliers) deflect and pitch up is commanded so you dont bust atc speed restrictions and protect yourself from the odds of a bird strike.
Window heat is also increased.
The NG is really top:ok::ok:
Avoid flying at high speed for a long time in areas of bird activity is recommended,if the bird is too big you can always duck under:E
Aircraft management is good,saving gas is even better,high speed is not required for either.

[framer]

Underfire Pinhead and Huck, why don't you spend thirty seconds looking in the Limitations section of your FCOM? There is no such limitation if your window heat is working.
This place has been over-run by simmers I fear.

[zac21]

if the bird is too big you can always duck under!!!!

Not in my airplane,,, we never "duck under a bird",, always over or around as a bird will dive every time from our experience.

[de facto]

oh my god.
ok,ill rephrase....you can always brace brace brace:E:E:E:E

[GlueBall]

Speaking from experience, there is little difference between hitting a bird at 250KT and 350KT.

...explain that to NASA where a piece of separated FOAM insulation had punctured a hole in the left wing of Columbia. :ooh:

[RAT 5]

To those who fly high speed below FL100.

Much might depend on the environment you are in. It an not be an 'every-time' thing. What do you put in the FMC as XYZ/100? If you left 250/100 and then fly hi-speed it is almost certain you will need speed brake lower down. I always let the F/O's find out for themselves that is the case. I then ask them if they accelerate towards red traffic lights and slam the brakes on or coast in idle towards them?
Various pilots I've known made calculations of a normal VNAV descent from FL200 with 250/100 and a CDA low drag to spool up at 1000': and a 300/100 descent profile. The time saving was miniscule. The stress of "have I got the right?" was removed and any turn radius was much reduced. Being 220kts downwind allowed flaps and a shorter turn-in; saving time. 300kts down wind made for a longer/wider circuit.
There are macho's in a positive manner and there are those in a negative one. It's a good idea to decide which camp you fall in. IMHO.

[OhNoCB]

Curious: I flew for one operator (B737) who was on a fuel saving spree. The CI chosen gave 245kts in descent after mach changeover. They still manually entered 250/100. How daft was that??!?

Apologies if I am missing the tone in this, but surely that makes sense (albeit over a somewhat pedantic 5kts) as if they leave it alone they will have a decel point at FL100 from 245>240.

[Capn Bloggs]

What do you put in the FMC as XYZ/100?
You put in 210/3000 or whatever the limit might be. :ok:

[Cough]

OhNoCB - Point being - If 245kt is optimal for lowest fuel burn, why then increase the speed below FL100?

Rat 5 - I agree with your last point, but was taught it in a different way - Never fly fast away from an airfield...

[Pin Head]

Thank you for the replies. That's the beauty of PPRUNE, we are globally connecting as operators in our magnificent industry.

I am sure the founder, Danny Fyne will be proud of this and create discussion of items that are not really mentioned in official documents and non official ones.

From Europe, I personally know and witnessed that our founder would have conducted many high speed descents. Yes agree that workload can rise if not properly briefed, managed and flown but at the end of the day we have to be efficient in what we do behind safe and secure.

I question why they are not deemed efficient even though the thrust levers close at ToD and as part of a CDA possibly spool up at 1400ft all to become stable. Lowering the EGTs and saving fuel make them all worth doing and also makes us fly the a/c, which truthfully is becoming a lost skill.

In Europe many a charter outfit have save thousands of pounds in the process and have at times saved airlines from bankruptcy by being a sound effecient pilot.

So back to the original question, assuming no ATC speed restriction and deletion of 250 below 10000 there is no restriction on the NG?

Thank you

[ImbracableCrunk]

Vmo is 340. fini.

[Huck]

Underfire Pinhead and Huck, why don't you spend thirty seconds looking in the Limitations section of your FCOM? There is no such limitation if your window heat is working.
This place has been over-run by simmers I fear.

Simmer? Lordy.

Actually I'm a 767F captain.

But I was an MD-11F captain when I hit a bird outside Quito at 330 kts. Terrain was around 10k msl so we were definitely in birdstrike territory above ten. Cost the company a radome and a bunch of other damage.

I've also hit a bird at 250 kts in a King Air, hit another at ~170 knots in a DC-10, and at 130 knots in a 767, last month, in the flare at Changi.

With a wide spectrum of data on this, I do 250 or less below ten. Always. Maybe above ten if the terrain is super high.

[Mikehotel152]

I don't buy the 'cost saving' line, lest we ignore Boeing's cost index. Whenever I've seen it done on the line, the driver was a pilot who thought flying faster was a sign of skill. The same people always find themselves hot and high.

I prefer to 'see and avoid' at <250 kts under 10,000 feet. I'm obviously uncool.

[RAT 5]

I don't buy the 'cost saving' line,

Years ago it was shown to me, via paper calculations, that descending at hi-Speed below FL100 does not save fuel or time; therefore is not more efficient. Hi-speed from TOD does save time, if you get it correct and ATC does not intervene. It can be very embarrassing if you 'plan/brief' a hi-speed descent from TOD with no buffer an ATC turn you in shorter. Up creek with no paddle and sweaty palms come to mind. Speed brake the whole way, gear out early, flaps out on limits and a dive in landing config. Do it once and never do it again. Was it really worth it? You could ask ATC for more distance; so they put you in sequence behind a heavy, instead of in front, and your 'more efficient descent' just went to the opposite.
Easiest way to save time & fuel is a shorter turn in with a CDA to 1000'. More relaxing for those down the back, and certainly for those up front.

[Avenger]

Underfire, the FMC speed coding to 240 its below FL 100 is nothing to do with ATC, its a VNAV coding to allow deceleration. :

Normally, the target speed is economy speed above the airspeed restriction altitude and 240 knots below that altitude, until deceleration for approach. VNAV will not permit descent below the airspeed restriction altitude until the airspeed is at or below the restricted value plus ten knots. The start and end of the airport speed restriction deceleration segment is shown on the map as a green open circles with no labels.

12-11.31.24 B-737NG Operations Manual Part B 38/26 SEP 13 Volume 5

[framer]

Simmer? Lordy.

Actually I'm a 767F captain.


Sorry Huck, I read something into your post that wasn't there.

[Mikehotel152]

Rat 5

I bow to your greater knowledge. I was merely going on my understanding of the basic Boeing CI, which will give climb, cruise and descent speeds to prioritise money over time, or vice-a-versa.

With CI 30 giving a 270 kts idle descent and CI 6 giving 245 kts, one presumes that the earlier TOD and slower idle descent is more efficient in terms of cost. Naturally, without ATC interference and with wholly correct FMC inputs, both would theoretically give an idle descent to the final approach.

Ergo, maintaining high speed below FL100, unless the restriction were removed before TOD, would burn extra fuel.

[Huck]

Absolutely no prob.

[ManaAdaSystem]

High speed saves time but will increase cost. In descend. Climb at eco speed below 10000 ft saves fuel.
I've been flying long enough to remember when there was no speed limit below 10000 ft. High speed was pretty much SOP, and it was not a big deal.
250/10000 ft was introduced by ATC.
So now high speed below 10000 ft is a near death experience?
I have an image in my head of white knuckled pilots with sweat running down their faces while they blast through the air at 280 kts. Are we going to make it?

Apparently, I'm lucky to be alive.

[Capn Bloggs]

Here, the main use of "above ECON" speed is at ATC request to make the inbound flow work better. It might cost a bit of fuel but will mean that I will not mess around possibly 5 aircraft behind me. Optimally, you'd clear the 250/10k before Top of Descent. If you can't, there are still benefits for all involved.

With CI 30 giving a 270 kts idle descent and CI 6 giving 245 kts, one presumes that the earlier TOD and slower idle descent is more efficient in terms of cost.
Only if fuel is expensive... Extra flight time costs money as well.

[misd-agin]

You guys using different physics than the rest of the world??

Of course high speed below 10,000 saves time. Using 310 kts instead of 250 kts from 40 nm to 20 nm saves you .9 of minute.

Speed vs altitude is the name of the game. 250 kts at 10,000 at 40 miles to go, is a great efficient and quick energy fix. Crossing it at 310 kts means you'll have to use drag to get rid of the excess energy. Here's the solution - for every 30 additional knots be approx 1000' lower. IE - 280/9000/40 and 310/8000/40 are about the same total energy.

You can double check this by removing the FMC's 250/10000 restriction and inserting a fix at 40 miles to go. Then put the different descent speeds on the FMC's descent page and see how much lower you'll be for every additional 30 KIAS. It's about 1000'.

There are places and seasons where I don't do 'high speed' below 10,000. The majority of the time it's John Daly time - "grip it and rip it." (Don't overthink it, just do it)

[nick14]

250/100 is a speed restriction due to airspace. It also helps prevent High energy approaches.

Putting 250/100 in the FMC does not make it increase speed from CI6 245 to 250. It merely allows for the airspace speed limit/company limit to be adhered to if we are asked to fly faster than 245 above 100.

[misd-agin]

If you ignore the distance to the runway 250/10,000 does not reduce high energy approaches. 250 kts below 10,000, at 5 nm to go, is too much energy. 250 kts below 10,000 at 50 nm to go, is an easily managed amount of energy.

It's a three headed monster - speed, distance to go, and altitude. The various combinations provide a low, good, or high energy state.

[Mikehotel152]

Easily managed can go to 'ah, bugger' quite quickly in busy airspace!

Only if fuel is expensive... Extra flight time costs money as well

Yep, the appropriate cost index should vary between airlines, aircraft types and even routes. Here in Europe, fuel is a high cost, so the CI is often low. In my airline, salary and maintenance costs are tightly controlled, hence they're less important than fuel. Moreover, there's little emphasis on scheduled arrival times in my company, so they'd rather we stuck to the most fuel efficient flight profile.

[de facto]

and then connecting passengers issue joins in the party of the CI..

[underfire]

framer, sorry, but the system defaults to 240kts below 10K in VNAV. If you bust 250kts below 10K, it will go to LVL CHG. I do get to do quite a bit of sim work, first desktop, then the full motion to test RNP procedures.

737 FCOM: 11.31.34
http://i.imgur.com/bparzaR.jpg
http://i.imgur.com/u4V5zH5.jpg
http://i.imgur.com/O8FLYYd.jpg

[WhatsaLizad?]

Somehow I'd guess 3/4 of this lot could not manage an idle descent from altitude to save their lives without furiously typing requests to the VNAV gods.


As for the high speed at lower altitudes, it depends. My need-for-speed is tempered by the pics of one of our 767-300's that took multiple bird strikes >10K out of CDG. I believe the speed was north of 340KTS. The jet looked like it took more than a few rounds of 20MM cannon hits along with a bloody carcass that punched through the left forward cockpit pressure bulkhead and ending up splattering over the Captain's flight bag.


4-5 lbs birds, but my memory is a little weak on actual size. Choose wisely, Tweety doesn't have TCAS. :E

[framer]

framer, sorry, but the system defaults to 240kts below 10K in VNAV. If you bust 250kts below 10K, it will go to LVL CHG. I do get to do quite a bit of sim work, first desktop, then the full motion to test RNP procedures.

I can see three different possibilities Underfire;
1/ you were in a rush and what you wrote above was in error.
2/ you operate FMC updates that are fundamentally different to any I have seen since 10.4
3/ You really shouldn't be validating RNP procedures for any passenger carrying airline until you understand the basics.
Which one do you reckon?

[vapilot2004]

Somehow I'd guess 3/4 of this lot could not manage an idle descent from altitude to save their lives without furiously typing requests to the VNAV gods.


While the programmer boffins surely appreciate the promotion, am I not alone in nearly always having a rough idea in mind for cross check, just in case 'ye gods' have gone mad? And for those times when it's not perfectly clear, a visit to the altars of Father Time and Maths should help the lost find their way.

[framer]

I'm with you VA. My experience is that about once a year it pays off.

[underfire]

I can see three different possibilities Underfire;
1/ you were in a rush and what you wrote above was in error.
2/ you operate FMC updates that are fundamentally different to any I have seen since 10.4
3/ You really shouldn't be validating RNP procedures for any passenger carrying airline until you understand the basics.
Which one do you reckon?

Nice reply, I expected no less from you. We have to design procedures with the lowest common denominator in mind. There are ac running these configurations. (as noted by the FCOM screenshots)

There are plenty of other posts referencing the 240kts as the default on Boeing ac. Most pilots also rumble that it is to prevent a bust below 10K.

What is your take?

[Derfred]

This thread should be deleted, quickly, before anyone else reads it.

[framer]

Nice reply, I expected no less from you.
Yip that's a fair call. I wouldn't have said that to your face so I shouldn't have said it here. I apologise.
I don't think anyone is disputing that the system defaults to 240kts. Certainly not me.
the system defaults to 240kts below 10K in VNAV. If you bust 250kts below 10K, it will go to LVL CHG
The above statement is incorrect. The only time it will go to LVL CHG is if you get very slow, pretty much the opposite of the scenario you describe. It is possible that there are FMC logic variations floating about that I have not come across, if that is the case I'm standing by to learn something.
Again, apologies for being a rude grumpy pr1ck.

[Mikehotel152]

This thread should be deleted, quickly, before anyone else reads it.

Sorry to sound naiive, but why?

Seems like a pretty lively discussion, some of which may have missed the point of the original query but garnered a bit of interest.

[underfire]

framer, no worries.

According to what I understand, VNAV will revert to LVL CHG to prevent overspeed. As you state, there are many possible combinations and options to consider. That is why I enjoy these conversations, and there are many combinations that are difficult to consider. Field operations, has exposed many, many issues.

As you stated VNAV will disco to LVL CHG if the ac goes below min speed, but my understanding is that VNAV will disco if you go overspeed with gusts (hence the 240) It also may disco to VNAV SPD on overspeed. In reality, I am unclear as to gust overspeed vs overspeed, based on what I have experienced.

Perhaps this is where the confusion comes in, at least on my part, but, what I do know is that it is a problem (or at least was) when you code a waypoint at 10K with a speed restriction of 250kts on the B models. Airports and the advance of procedure design,...the coding itself has introduced anomalies that had never occurred before, such as a RWY point over 10K, the box just could not do it. (the damn 10K is hard coded and buried in the code of so many areas...)

Regards

[underfire]

The Vmo of the 737NG "here" below 10k is 340, as it is with my "little Boeing".

just curious, looking at the CASA regs:

http://i.imgur.com/aO4ghlh.jpg
http://i.imgur.com/YMZSUSi.jpg

just how much of the airspace below 10K can you drive over 250 kts?

[Capn Bloggs]

It's the regs, underfire. :cool:

[misd-agin]

Underfire - class E, first line, ends with an *. What does the statement next to the * say?
That's usually where the exception is made where 250 below 10,000 is approved.

[Denti]

Apparently Class C for IFR traffic. That seems to cover control zones and the associated steps leading to that airport.

Anyway, it seems kinda similar to how it is over here in germany, below 100 it is allowed in Class C and whenever approved by an ATCO in protected airspace (Class D not Control Zone for example). But companies can have stricter limits, mine for example has a non type dependent general speed limit of 250kias below FL100 except if a specific higher speed is asked for by ATC (high speed approved is not enough), however 250kias is an absolute limit 5000ft and below.

[RAT 5]

But we are back to the basic question: not of if it's allowed by the regs, and often it is not, or SOP's, but does it make good airmanship common sense in most cases? You CAN do lots of things, but is it necessarily a good idea.

[LeadSled]

Folks,
Re. the FMC default 240/10,000.
The US speed limit is MAX 250 below 10,000, there is no +/- 10, or any other tolerance that is applicable in many jurisdictions, this point has "sort of " been made.
The US speed limit is a statutory limit, FAA ATC have no authority to give you a waiver, but there is the authority of the PIC under the rule FAR 91.117(d).
Tootle pip!!
PS: Don't pick me up on some of the trials of greater than 250 below 10, they were approvals by the Administrator per. FAR 91.117(a), not ATC.

[Skyjob]

FMC defaults to 240/FL100 for ONE reason: VNAV will NEVER exceed 250kts below FL100!
VNAV allows for +10kts faster to be flown, thus defaulting to 240 ensures compliance.
Conversely, the A/T "wakes up" when VNAV gets -15kts below commanded VNAV speed.
Use the systems as they are designed, in parallel, and we end up with an aircraft idle descent not exceeding limitation...

Regarding CI, as mentioned in this post:
1) CI for descent is linear between KIAS and CI, hence low CI relates to low KIAS, 6 being 245, 0 being optimum glide for fuel at 239.
2) CI for CRZ and CLIMB take into account many more parameters such as weight, level, toc wind (calculating a speed correction for the calculated hw/tw component 150nm along the track direction after takeoff by using the angular difference between the track and toc wind direction), toc isa, to name a few...

[misd-agin]

Rat5 - But we are back to the basic question: not of if it's allowed by the regs, and often it is not, or SOP's, but does it make good airmanship common sense in most cases? You CAN do lots of things, but is it necessarily a good idea.


Except for the USA it's typically allowed by the regs and individual companies have different SOP's, as Denti mentioned. So if the regs allow it, and the SOP's allow it, the common sense question is an opinion not supported by the regs or SOP's.

The answer to the question 'is it good airmanship in most cases' is yes, provided there aren't other reasons not too. Like specific arrivals that have known bird issues or during bird migratory seasons.