Reduced Runway Occupancy.

[forget]

Are there any pilots out there with a pioneering streak, an interest in Reduced Runway Occupancy, and who may have 15 minutes to spare with a Sim? There’s a proposed scheme, when landing, to give you ‘clear voice’ distance to go to the (next) exit. The ‘voice’ will give you, for example; ‘Rapid Exit 1,000 feet’ (metres). Exit 500 feet ----- Exit 200 feet. In operation there’s no change to the aircraft.

If anyone’s interested in giving it a go, and giving an opinion, I’ll post the very simple procedures. The system was assessed with a Sim some time ago (thanks to GN and JW if you read this :ok:) and the results were far better than expected but I’d like to hear a broader view.

[Rwy in Sight]

Is/was not that part of the ADS/B system that would "build" the decent profile as to make sure the touch down point and the breaking (sp?) were set in a way that allow the aircraft to vacate the runway as soon as possible?

Rwy in Sight

[BOAC]

Forget - I had 'forgotten' our previous discussion on the earlier thread and I'm pleased the trials showed well. I'll let my company trainers know about this and see if I can generate any interest. Have you tackled BA on this also?

[forget]

Rwy in Sight. Is/was not that part of the ADS/B system …….

No. Much less complicated. This scheme is an airfield installation, which means that, once commissioned, all aircraft can use it – without modification. See below.


Thanks BOAC. :ok: I’m asking for interested pilots to try the Reduced Occupancy scheme in a Sim because we need to get more input/opinions from the sharp end. The mechanics of getting a clear voice message to the cockpit via the Marker Receiver are well proven. Although it appears obvious, we need to know just what benefits landed pilots would derive from hearing accurate Distance to Go to Exits. We need positive feed-back from ‘end users’ before we can get airfields interested.

The previous Sim trials results are Here (http://www.axis-electronics.com/pdf/gm_reduced_runway_occupancy.pdf) with responses from high time ‘Heavy’ captains. Note - “The results are remarkable! The runway occupancy times in these Cat 3 conditions match what I would expect to see in clear visibility. There is a definite feeling of more control because of the increased situational awareness. This also means the Auto-Brake settings can be reduced for increased passenger comfort and decreased brake wear. I can think of no circumstances where this would decrease safety”.

We've not spoken with BA but please PM me if you’d like the details of the Sim procedure.

[BOAC]

I'll leave the detail of the sim for others, forget, but I'll bring your thread to the attention of my company. I have to say, though, that if we are to get 20 seconds average which according to your figures equates to only 4 to 6 more movements per hour, is it really worth the effort/cost involved? Bear in mind also my point that you will not get those reductions in ROT from all crews either. I note that HD reckoned (in the previous thread) that these reductions would be 'lost' in the take-off spacing requirements, although I still cannot see that.

Incidentally, is '26left' still on frequency? PM contact appreciated.

[PEI_3721]

IMHO such as system should be considered with caution.
IIRC a reduced runway occupancy trial was evaluated in Europe (Munich?) resulting in a reduction in safety. The trial did not involve equipment, poor visibility, or have the same objectives; but in raising awareness and the need to exit the runway as soon as possible encourage rushed procedures and fast taxing. There may have been additional hazards in negotiating taxing patterns with early turn offs or having to hold before crossing after a high speed turn off.

The reports from the new system are extremely narrow and may not apply to other operations. Apparently, only non limiting runways were used without variability in braking conditions, - two critical features in Cat 3 (indeed in all operations). It would be foolhardy to state that safety would not be degraded at the same time as reporting on a system which encouraged reduced brake wear and lower auto brake levels; compare what is proposed with today’s balance between economics and safety – the current accident rate.
Some of the hazards of auto brake use have been covered in other threads, but anything which appears to reduce the levels of braking where the industry’s leading cause of accidents (hull loss) is due to overruns might be judged unwise.

However, from the system description there may be benefit in improving awareness of the achieved level of braking – the rate at which marker boards are passed; particularly in low visibility. If so, then this could overcome some problems on low friction surfaces where the anticipated auto brake level is not providing the required deceleration, thus enabling full manual braking at an earlier point – within the margins of safety in the calculated landing distance.
A similar advantage might be seen for operations on limiting length runways by providing awareness of what distance remains to the end of the runway. This type of information is provided by systems such as RAAS, but the new system has the advantage of an airfield installation applicable to all aircraft.
I would prefer to have a system which reduces the risk of an overrun before providing greater airport capacity; necessity before nicety.

[Dan Winterland]

The A380 has an 'Exit by' function where the crew specify which exit they would like to use, the autobrake deccelerates the aircraft to 50 knots by that exit.

[forget]

Thanks PEI_3721, useful points for discussion. However, you say It would be foolhardy to state that safety would not be degraded at the same time as reporting on a system which encouraged reduced brake wear and lower auto brake levels. .....anything which appears to reduce the levels of braking where the industry’s leading cause of accidents (hull loss) is due to overruns might be judged unwise.


I don’t quite follow this. It infers that maximum landing safety is always dependent on Max Autobrake. No?

Also, from Dan’s input, the A380 uses its own brains to produce the minimum brake levels (optimum deceleration) to arrive at a chosen exit at 50 knots. The proposed system supplies the pilots with the audio information to do this under their own control, after allowing initial Autobrake.

[Musket90]

Gatwick has RETILS (3-2-1 countdown lights) installed on 08R/26L RET's to help keep occupancy times down. Not sure how effective they are in LVPs. As for runway capacity on a busy mixed mode runway in LVPs, ATC need to ensure arrival spacing is sufficient to ensure that ILS integrity is maintained for consecutive arrivals and for departures between arrivals so if it cannot be guaranteed that arrivals will achieve the desired exit then until ILS is replaced I can't see any benefits for runway capacity as arrival spacing will remain unchanged. The only benefit perhaps is giving a slightly earlier landing/take-off clearance to the following aircraft.

[PEI_3721]

forget re the inference: “… maximum landing safety is always dependent on Max Autobrake.”
The safety aspects during landing are maximised with full braking (in some aircraft manual is greater than Max Auto); this leaves the entire safety factor distance available for an unseen eventuality.
In practice pilots judge the prevailing conditions and apply brakes according to their planned action – usually much less than maximum, balancing their perception of a safe stop against other operating issues. Unfortunately human judgement, perception, and planning can be incorrect, which if detected the pilot adjusts the level of braking during landing. On rare occasions, no or late detection of the poor judgement or lack of runway distance (time) remaining results in an accident.
With autobrake, some of this judgement is removed (remote) from the pilot, e.g. lack of foot-force feedback. Also autobrake hides the brake contribution to the deceleration vs that coming from reverse thrust; in some conditions autobrake applies maximum braking, but this and reverse are still insufficient to achieve the required deceleration (misjudged / mis assessed slippery runway).
Overall higher levels of braking maximise safety.

Re A380; I am not familiar with the system, but I suggest that it might suffer similar problems as above.
If max brake/reverse is being used to defend against the possibility of a slippery runway then the aircraft may not stop at the required exit; how/when do the crew detect this, when do they intervene ( I presume that the aircraft does not know the exact runway condition – the same as a pilot).
In addition there is opportunity for input error. Supposing the safe default is the full runway length, then in extreme, the ‘low’ braking level applied to achieve 50kts by the end would reduce safety. Again how and when do the crew become involved?
Involvement requires a parameter for perception and judgement; with manual braking the foot force / deceleration, visual scene loop provides feedback, but with autobrake (fixed or controllable levels) the loop is weakened or broken – particularly in low visibility.

The industry’s safety problem involves human perception; if the new system helps perception of marginal landing performance then there is value in the development. Unfortunately many airlines think that they are safe enough.
Selling the idea to airports may be more attractive, but they may not match safety with the opportunity for enhanced revenue.
The alternative is to ‘sell’ the idea to the regulators, as they might have a more balanced view of any benefits (yet to be shown) for improving landing safety.