What can controllers see?
 

Coming back in to a London airport this week, the director asked us to slow down to an assigned speed - due traffic ahead, which we could see on tcas. My colleague on the flight deck selected the speed but left the aircraft in vertical speed mode (V/S) which kept the descent going and the speed 30kts higher than asked, instead of using level change or open descent (Boeing/airbus). No more than 10 seconds later the director rightly asked us to reduce speed again, only this time to actually reach the speed requested!

My question is - what information can the controller see on his or her screen. In this case the correct speed was selected but not flown. I am also led to believe that the level set in the alt window is also visible to the controller, is this true?.
Best wishes,

Marvo

If you have Enhanced Mode S, UK Centres at Manchester and London can see Selected Flight Level, actual heading, actual IAS, actual rate of climb/descent, actual groundspeed, and aircraft ID.

Scottish Centre get the capability in December.

Marvo
If you are asked to fly a specfic speed due tfc ahead, why do you fly a speed that is 30kts faster than the speed requested

opnot
Good question. They saw the traffic on tcas yet elected to fly 30kts above assigned speed. What was the point of the exercise there? See if they could land on top of the other guy?

He probably used the infamous "TCAS separation".

"traffic eleven o'clock 8 miles, one thousand feet below, report traffic in sight"
"tcas contact, request visual approach"

Not an awfully good idea, Marvo. Modern technology is very clever but an experienced radar controller will quickly know if you're not playing the game!

A word of advise
 

I don't really know for the rest of the world but where I'm right now we usually have once a year meeting with a group of pilots and discuss this things just to explain them what is seen on the screen and that lying or not adhering to the instruction doesn't help at all.

After the first "seanse" most of them requested to visit the ACC and sit on the "jump seat" between the two controllers.If we can do it so should they.

Marvo,find some controller to get you in some ACC and explain you what is going on on the other side of the frequency,that will definitely help you.

To be honest,here we communicate much better after this meetings.

Cheers all,

Gianni

Marvo -
By the way - the director did not ASK you to reduce speed, it was an instruction. Speed control is just that - control. It is not called "speed advice".
Also - yes on radar, a lot of units have a lot of information displayed on the screen, but to be honest I don't need a read out of the speed to know whether the pilot has managed to press the right buttons and slowed down - I (and every other approach controller!) can tell whether aircraft have slowed or not by the distance betweens the radar returns.

The flip side of this is crews who don't tell the controller that they plan to slow right down on final approach, slower than instructed, thus reducing separation behind them. By this time they are usually on the tower frequency. I will send around the aircraft who is unable to fly the assigned speed and can't be bothered to tell the controller rather than punish the chap behind who has done exactly as instructed.

Controllers can work around anything the pilots are unable/unwilling - but only if we are kept in the loop, in sufficient time.

louby

We don't have mode S where we are but we see groundspeed depicted very accurately on our screens. If you're in the same wind band as another aircraft that we're applying speed control against, it's not hard to see when someone's cheating because the groundspeeds show a lot of variance.

When we determine who's doing the cheating, it can make for some interesting comments and vectors:ok::}

A lot of you have jumped on marvo, have you actually read his post? He wasn't the handling pilot at the time, and the point being made is that although his colleague selected an innapropriate mode of descent to achieve the requested speed promtly, there was very little time between the initial instruction and the follow up from the ATCO. I'm sure marvo would have said something had he been given time. It is useful to know you guys have all the info with the enhanced mode S, as it is blatantly obvious that some pilots, particularly at places like lgw, are not flying asssigned speeds, which completely wrecks the sequence causing problems for everyone.

Again using lgw as an example, it is a regular occurence that we may reduce from 220kts back towards 200-180kts on a loc intercept heading. This is nearly always due to a high workload for the controller resulting in a late instruction to reduce, and a busy frequency making it hard to get a call in, so we pre-empt slightly. Reducing below 170kts only ever happens once we are through 6dme (company policy - ezy).

I think speed control at later stages in the approach is sometimes badly complied with from our side of the fence because we regularly get left fast and often high on profile by some European ATC agencies who ask for "enthusiastic" speeds and then neglect/forget to cancel the restriction until it is basically too late, so slowing down without the nod from ATC, often a requirement when operating in some parts of Spain and pretty much the whole of Italy, becomes commonplace if there is any doubt that we are going to meet our stable at 1000'/500' policy.

Unfortunately not every country offers the level of ATC service we get throughout the UK. If you can get a jumpseat ride, get on a sector to Pisa - you'll be amazed at what ATC there expect us to do. The basic laws of physics and gravity don't seem to figure much in their MATS!

People, Marvo gave you the reason in his post....

He selected the incorrect mode, not deliberately... and the mode selected does not, necessarily, control the speed. Vertical Speed mode is a strange beast. It has it uses, and it also has its pitfalls.

Totally unfair on Marvo :ugh:

KK APP? High workload? Busy frequency? Shurely shome mishtake....:E

"What can controllers see?
Everything. :E

I see dead people.

Maastricht told me last week they could see what magazine I was reading. That started to freak me out a bit. :uhoh:

L337 -

Maybe Marvos' colleague needs some more sim time to fully understand the implications of switch selection (or non switch selection in this case)

Ther really is no excuse for a pilot not to know that leaving the A/C in VS mode will mean an inability to comply with a speed instruction in a timely manner (an instruction that is used not only for sequencing, but for safety).

Admit it, you were only looking at the pictures.
We were wondering how the threesome on Page 12 got into that position. :eek:

I know that this didn't happen in this case but it does amuse me when pilots think they can cheat the system and not slow down when told. The fact is that the landing time will be the landing time and it is slow down, hold or fly more track miles with vectors.

Having said that though I do find that the pilots in Europe are far more accommodating of speed control than their colleagues in Australia. I'm not sure if it's because of traffic density or expectations but it certainly makes life easier when everyone does as they’re told.

Give the guy a break. I'm tired of people on this forum jumping down peoples necks for their comments. At least he bothered to ask.

If ATC ask me to climb/descend slow down/speed up I do it!!!.....Let these guys do the job they are trained to and hopefully then they will allow us to fly the aircraft!! For someone to be asked to slow down and then still fly +30kts on the requested speed is pretty dam crazy!!...Come on guys ATC have it hard enough lets give them a frigging chance!!

RTFP, eh?

So many "holier than thou" folks on here.....

Yet again a poster asks a question but gets jumped on.... :rolleyes:

Good job us controllers never make a mistake. Or bend the rules. And that we always know everything about the equipment we use....

Spitoon.....your jobs hard enough without some folk flying around with their heads up their arse's....keep up the good work :ok:

Thank you to some for your posts, especially Right Rudder. This has motivated me to sign up to a truce day at Swanick!

Whilst I was not the pilot flying I am sure my respected colleague was aware of the aircraft mode selected, and although it was not the mode I would have chosen, I was about to remind him of the speed requested. The Boeing, naturally ,does have mode S so you can see the speed and alt- thanks for the info.

I feel privilaged to be among experts!

Marvo

It's called the lion's den for a reason. Failing to comply with speed instructions is a big no no, even if you're not the pilot flying. Anyone heard of CRM.

Spitoon

Marvo has just said Sorry, but a mistake is a mistake, and if he had selected the wrong mode in error that's fair enough - but this is not the case here (it seems) and not knowing the implications of a selection when flying an aircraft is not really good enough.

Your quote is slightly out of context - it's not a case of knowing the engineering behind the equipment, it's about knowing what the equipment does in real terms when you use it!

Unless things have changed since I flew for a living, most pilots will have to learn and understand in some depth about the systems they are using, including down to the nitty gritty of studying and being able to put into layman's terms, the circuit diagrams of major systems etc.

Not knowing, or possibly disregarding the fact, that certain mode selections means an inability to comply with an instruction is not good enough as Tarnish, a current professional aircrew poster, has pointed out above.

A great topic and one that is very worthwhile discussing - lots to learn on both sides, I feel.

I'll make a few points. I've worked on both sides.

I'm generalising - but from the centre's and TCA's/Approach units I've worked in - I find the following to be true.

1. To answer the original question, even though LATCC can see both selected and indicated airspeed, I'd venture that 10 seconds is a rather spritely time to jump on a perceived inadherence to a speed instruction.

2. Speed Control, for the majority of controllers, and in particular Centre/TCA controllers is at best a rather imprecise science. When the aircraft is in level flight, a la final approach, or en-route, great - apply your 160's and Mach 0.78's and expect lateral spacing accuracy - magic. Initial descent into an airport, however - 'suck it and see'. How do we make this work as controllers? 9 times out of 10, ask the lead guy what he's doing (270 kts) - restrict the guy behind to the same or slower speed. Works, but its rough science.

Fact is that from FL300 down to FL100 the changing levels, winds, IAS/TAS relationships, Mach/IAS crossover, etc. etc. make the speed control a little loose.

If you're a controller - try this - next time you're sequencing for the initial approach, take a guess at what the mach number or IAS is before you ask ... often far different from what you think.


3. Mode Selection and time to achieve assigned speed. If I'm on final, and can see a guy 3 miles ahead, I've got my ever-ready trigger finger on the speedbrake - ready to achieve that 180 or 160 knot restriction in seconds ... however, if I'm descending through FL210 and get a speed reduction of 60 knots - lets say from 280 to 200 ... that reduction is going to be slower. I'm certainly not dirtying up the airplane to achieve the restriction ... it'll happen at a nice even rate (I believe the Doc 4444 ideal is 1 kt per second, I could be wrong).

I can achieve this reduction in a variety of modes, independent of aircraft type - V/S, LVL Change, whatever .... one is not necessarily any different from another depending on the current speed and config., in terms of achieving the speed required.

4. The Mach/IAS changeover is the biggest hurdle to accurate spacing, from what I've seen. Today a perfect example, controller asks what's your Indicated speed .. colleague replies "255 kts" ... great, ... guy behind is told "250 or less indicated ..." ... Great except that we are at FL320 and 255 is actually pretty fast ....

To make it work ... with perfect spacing ... tell both guys to fly, eg. Mach 0.76, transition to 280kts on indicated .... you'll keep the spacing all the way, as we will both have the same crossover, and the same groundspeed is guaranteed.

5. The "Lie"

Trust me, this happens far more rarely that you think. Hell of a lot less than controllers lie to pilots :E. Kidding.

But they key is that there are 2 guys in the cockpit. And neither is likely to say to other, hey - I know ATC just said slow it up - but f%ck it ... lets keep doing 250 and see what happens. A very simple reason - but its very unlikely that you'll get two jokers flying together. Most - even if they want to get home early to see the football - will dial in the 220 knots immediately - and select a method of speed reduction immediately - and the other guy will say checked and we all go home without any report writing.

6. The go down and slow down

Ok so its old hat, we all know it, but it really is true for most airplanes - and most airplanes are built with pathetic excuses for speed brakes. If you're within flap limiting speed you can also chuck out a bit to slow up - but often slowing up quickly is difficult .... especially at higher alts.


Just a few random thoughts .... keep 'em coming! :}

I am reminded of the american DC10 freighter crew some years ago who did not have QNH selected while being vectored for the ILS at East Midlands with an extremely low QNH. They ended up dangerously low.

Can you see the altimeter setting with mode S or just infer it from the display e.g. the aircraft is a multiple of 30 feet below a minimum altitude.

My particular bugbear at the moment is being cleared to decend to a level below flight level 100 with 2000 feet per minute all the way down. The problem is that at normal speed say 290 knots there is no way I can descend at the given rate and reduce speed in a sensible fashion to the mandatory 250 knots. This happens to me all the time descending into a particular airfield in airspace E. I have lost count of the number of actual RAs I have had in this airspace so it is something I take very seriously.

When I point out that I am unable to comply with the clearance or inform ATC in advance of the problem that is going to occur there is seeming incomprehension and a sense that I am telling them how to do their job.

Excellent post Marvo, lots of useful information from both sides. :ok: