Why do some pilots consider speed control to be optional??

[GlueBall]

PSR...

I concur with judge.oversteer that large heavy a/c have speed/flaps issues, which is to say that having to manoeuvre with flaps extended in order to comply with a slower speed multiplies fuel burn, and after a 14 hrs flight there isn't much "extra" fuel to be dragging flaps.

There is no excuse for non compliance, but controllers should also be conscious of performance constraints when ordering a 747 to reduce to 220kts when 50 miles out.

[MrHorgy]

Rocketing around at 320 kts at FL170? What's to be achieved with this on such a short sector? You'd save one minute at most probably, which you might lose if you were given delaying vectors...

[Trim Stab]

I expect I'll get flamed for this - but when asked to slow down we try to comply as tardily as we think we can get away with (similarly, when asked to descend too early for optimum profile).

Margins are so tight in corporate flying at the moment - the only profit we make per flight is what fuel we can save compared to that budgeted on the flight plan. In our company we are desperately trying to keep the company afloat and keep our jobs - so if we can save 50lbs of fuel, we'll fight for it.

If you think somebody is taking the mickey, just say the magic words - "slow to xxxknots, or expect a hold at yyyy"!

[NigelOnDraft]

I make all efforts to adhere to ATC speed requests. However, I do wish sometimes ATC understood:

1. Being asked to speed up to >300K in the same sentance as "expect 10-15mins delays" is just asking my employer to tear up £50 notes in quick succession.
2. Asking someone, from level flight, at say 270K as requested, to lose 10,000' in 25NM, with a tailwind is just not going to work.
3. Asking us, directly or indirectly, to break the TCAS V/S limits is going to be refused.
4. I will refuse to go >270K in turbulence if I judge it unsafe, or even unnecessarily uncomfortable.

I appreciate pilots will have different speeds they wish to fly - but I think ATC have some responsibility towards the planet and not burning fuel totally unnecessarily

[RomeoTangoFoxtrotMike]

[ Disclaimer: I am not a pilot or ATC ]

Surely, if the circumstances described by NoD, or others, apply, the pilot should respond "Unable" and hopefully add "due [reason]" as soon as possible, to give the controller an opportunity to come up with a new plan, rather than silently disregarding, and making him and everyone else guess... ?

[DBate]

I concur with judge.oversteer that large heavy a/c have speed/flaps issues, which is to say that having to manoeuvre with flaps extended in order to comply with a slower speed multiplies fuel burn, and after a 14 hrs flight there isn't much "extra" fuel to be dragging flaps.

There is no excuse for non compliance, but controllers should also be conscious of performance constraints when ordering a 747 to reduce to 220kts when 50 miles out.

All correct, however there is no reason - when given a reduction to 220kt by ATC - not to ask ATC if you may 'maintain 230kt to stay clean'. In my experiance that request is usually granted unless the controller really needs you slower.

Point is, if a specific speed intruction is given, then we are to comply. Airspace nowadays, especially in Europe, is way too crowded. Instructions by ATC are given for a reason, and usually it's not just 'for kicks', but to avoid coming close to other traffic or for flow control. The whole system is at times operating at its limits, so lets not make our colleagues work on the ground (i.e. ATC) harder than it already is by not complying with instructions.

There is no room for 'personal interpretation' of a clearance. If you have doubts, then ask for clarification. My guess is that this is way more preferable than just doing what you think ATC wants you to do.

And regarding use of speedbrakes; it's a paid part of the aircraft. Why not use it when necessary.

[PSR]

The majority of my colleagues are aware of the difficulties speed restrictions can impose on flight crew (with regard to descent profile, turbulence, tail winds etc.) and try to take this into account. There is obviously, however, a vast difference in performance between aircraft types flying in/out of the UK, and we simply don't have enough detailed knowledge about every type of aircraft and what the pilot can/can't do with it. Therefore, the logic most people seem to use is to ask for what would be easiest and if the pilot is unable then he/she will say so (and most pilots seem to). Then we can sort out something different. This happens regularly when asking for level and speed restrictions at the same time etc.

Obviously there are different objectives the flight crew are trying to achieve in each aircraft (whether it be to save as much fuel as possible, or get to destination as quickly as possible), but when the airspace is busy everybody has to fit into it safely, and this will mean you could be assigned a speed of anything between 250 and 320kts typically to ensure aircraft remain safely separated. If you are unable to reasonably comply with the restriction imposed, then please say so. That is aftera ll what we'd expect you to do.

[con-pilot]

To be honest, I never gave speed assignments much thought. What ever was requested I did*. Now for speed reduction, I just used the throttles, not the speed brakes.

As the old saying goes, the speed brakes are for my mistakes, not the ATCs mistakes.

* Unless I believe that an assigned speed was unsafe for the conditions; faster or slower. Which rarely occurred.

[Sussex Kestrel]

As a professional you endeavour to do your best with speed constraints- if not, simply speak out- however (though my profile states that I can indeed hover at the drop of a hat) in reality whilst at D7 on the ILS maintaining 180kts (an atc instruction) being asked to maintain 160kts to D4 is, for most jet liners (though especially the 757), a pointless request- especially when in the clag with anti-ice on the go.
The two way understanding between ATC'ers and flight crew has improved over the years through, in my opinion, such liaisons as the latter visiting the former's workplace- seeing it all unravel, as it were. Controllers coming along on flights to see how it is put into practice would only help both communities acquire more of an understanding of both professions.........
Don't get me wrong, most of the controllers (especially at London's Sussex airport) are top class....

[Trim Stab]

To turn the tables...Why do ATC consider ack'd flight levels optional?

If we have filed a flight plan, which has been accepted and acknowledged with a stated cruise flight level, how do ATC justify holding us down at a lower level?

On more than one occasion, I have uplifted OPS-minumum fuel for the filed and accepted flight plan, then been held down below the planned flight level for a significant portion of the cruise meaning that we risk not having enough fuel for the flight. The answer is not - "you should have uplifted more fuel" - we fly to extremely tight margins and if fuel is more expensive at departure than arrival, we uplift the OPS minimums.

The whole point of OPS fuel regulation is that it should cover all forecasted eventualities with sufficient safety margin for safety - so how do ATC justify throwing a completely unforecasted spanner into the equation by holding us down below the planned flight level?

[J.O.]

Would you rather receive a 30 minute slot delay to ensure that you get your desired cruise level every day? ATC do the best they can, especially in Europe where there are more planes trying to share the skies than separation normally allows. Besides, unless the ATC are holding you down by an order of 10,000 ft or more, the contingency fuel in your flight plan should more than account for the different altitude. If it doesn't, then it seems to me that an ASR to your company would be a good start at correcting the overly tight fuel planning you're being asked to accept.

BTW, if you're flying in Europe in today's environment, it's pretty hard to say that a lower than planned altitude qualifies as "completely unforecasted".

[Cough]

Trim tab, sorry, no sympathy from me.

Sometimes we are 2000 ft lower, worst I've had recently is 4000ft lower. But the direct routings that ATC provide more than make up for the level (especially from Maastricht!). And if you think about it, to guarantee your level, ATC would have to ensure that a 100nm section of your route is clear for you to climb into (15 min slot window at 400kt) Now that's just plain greedy, but if we went that way, nothing would move due to it's slot!

Min fuel is all very well, but you already know what happens and should ensure your fuel uplift is enough to cover your expected flight, not some theoretical dream...

[NigelOnDraft]

If you are unable to reasonably comply with the restriction imposed, then please say so.

There are 2 issues with this. Firstly, the pilot using the R/T often reads back the "clearance" without being able to consider it i.e. the ATCO now thinks the restriction has been accepted.

(S)he now either realises that it is not possible / acceptable / suitable, or more likely, the PF (who really decides if it is) points out it is not possible etc. They will take X seconds to discuss.

Secondly, the R/T is now so busy they cannot get a word in to request / demand / refuse / amend that clearance, and by the time they do, the ATCO has given another aircraft or 2 clearances based on our aircraft's apparently accepted clearance.

I do not know what the solution is? But I do sometimes get the impression ATCOs think we just dial in these numbers (height, speed) and the aircraft just obeys with nil side effects. They do not realise we have *** all fuel, and using speedbrakes, or excessive speed, and then get vectored round the sky / go into the hold makes little sense, and can even be hazardous.

I must add that there are exceptions... and we have been advised of our descent speed / holding duration / descent restrictions 10-20NM prior normal ToD. We can then plan the descent accordingly, request appropriate ToD, and fit in with their speed / altitude / holding profile, whilst keeing things safe, economical & comfortable

[PSR]

Nigelondraft - that's a very good point and something I'll certainly bare in mind. I was always trained to give speed instructions well in advance on TOD to ensure, like you say, that your descent can be planned accordingly, and for the most part I do this (usually only unable to if traffic is bunched and all aircraft arrive at or past TOD at the same time, which happens annoyingly often).

My post wasn't so much referring to these sorts of scenarios. I was thinking more of the occasions when speed instructions are given well in advance of TOD (like with the B734 previously mentioned), but are still ignored.

Another example that springs to mind from 6 months or so ago was a business jet (C750 perhaps?) given a speed restriction of 270kts or less when he was cruising at FL400 and at least 30 miles from TOD. The pilot flew at mach 0.85 (or something similarly high) until FL230! IAS was around 340kts if I remember correctly. His excuse was he hadn't transitioned to IAS yet. This too makes no sense to me. 270kts or less is 270kts or less. It applies at any level, even when flying with reference to mach, simply meaning IAS never greater than 270kts. Perhaps I'm missing something but how can that be misinterpreted?

[PSR]

Trim Stab - filing a flight plan doesn't automatically give you the right to continuous climb up to your filed cruising level. If there is traffic in the way, which there almost always will be at some point, then you may have to level off lower temporarily. CAP493 states any aircraft already at your requested cruise level will get priority over you - that's the rules we work to. In the UK we will do our best to get you to your requested level as soon as possible. The only reason you wouldn't get it is if someone else who is on the same route is there already at that level, or if you've filed to avoid flow restrictions on certain sectors (but even then we'll often let you climb into the sector on an ad hoc basis when we can see what the traffic situation is like and make an informed decision based on that). I know certain other countries in Europe use blanket level caps for specific destinations, but I can only speak for the UK. There will however often be procedures requiring us to present traffic in such a manner to those other countries, preventing us from giving you your filed level. I hope that answers your question.

[Intruder]

I was always trained to give speed instructions well in advance on TOD to ensure, like you say, that your descent can be planned accordingly, and for the most part I do this (usually only unable to if traffic is bunched and all aircraft arrive at or past TOD at the same time, which happens annoyingly often).

Why revert to explicit control "way too late" when all you have to do is tell each aircraft in succession to 'plan to reach WPT at TIMEZ and xxxKIAS'? Then they can figure out how to do that.

I can't understand why there is so much manual manipulation of descent and arrival profiles when there are numerous STARs that have all that speed and altitude profile stuff built in. All that's needed is a time at the beginning of the STAR, and the rest should sort itself out. If that's not working, then have somebody rewrite the STAR so it does what you need it to do! While there may be occasional unplanned conflicts, the STAR should be a 90% solution...

[PSR]

all you have to do is tell each aircraft in succession to 'plan to reach WPT at TIMEZ and xxxKIAS'? Then they can figure out how to do that.

If only it were that easy. Maybe one day it will be that way, but there are so many factors working against us at the moment (air space design, encouraging neighbouring sectors to present traffic, A at a suitable level so that pilots aren't way above profile in the first place, and B to initiate some sort of streaming in advance rather than just transferring everything to us way too late and expecting us to do everything).

Unfortunately the routes I'm thinking of are on a political boundary (I guess that wouldn't be much of an issue in the USA) where there is little or no chance or achieving any kind of change for the better, certainly not in any time soon anyway. Until then we'll continue to struggle to make some sort of order out of the chaos, with everyone frustrated that we're asking them to achieve something they can only just, or maybe can't even achieve in the time/distance given.

[GlueBall]

Trim Stab

"If we have filed a flight plan, which has been accepted and acknowledged with a stated cruise flight level, how do ATC justify holding us down at a lower level?"

...The short answer could be that YOUR airplane is not the only one in the sky.

[The African Dude]

Hi PSR, interesting discussion, thanks for posting.

given a speed restriction of 270kts or less when he was cruising at FL400 and at least 30 miles from TOD. The pilot flew at mach 0.85 (or something similarly high) until FL230! IAS was around 340kts if I remember correctly. His excuse was he hadn't transitioned to IAS yet. This too makes no sense to me. 270kts or less is 270kts or less. It applies at any level, even when flying with reference to mach

We often receive "Mach xx and xx KT on conversion", so I can see how a tired or otherwise busy pilot could misinterpret the instruction - despite the obvious clarity in your request.

At my UK base we are very limited in descent by a mid-level restriction during arrival which often requires a higher speed down to around FL60 to get below the terminal limits. What a number of us cannot understand is why we are given standard speeds with 2 to 4 thousand to go before we are passed to approach, at which point the speed restriction is removed. (We of course appreciate that there may be other influencing factors that we cannot know of from the flight deck).

AD

[PSR]

AD

That would also be very difficult for me to understand as the design of each bit of airspace in the UK is so different and I only have a detailed understanding of the sectors I work. We do welcome visits by pilots to the centre as it can only be of benefit to all of us. Likewise we do look for opportunities to spend time on the flight deck, which I've managed to do a few times, and I must admit I've found it invaluable.