No Reverse Thrust On Contam Rwys For Ryanair

[Jambo Buana]

The IAA have stopped Ryanair from benefitting from reverse thrust credit on contaminated runway LANDING calculations as a reaction to the Midway accident. Have any other EU regulators enforced this yet?

This will have a huge impact on Ryanairs operations over the winter period!

With a full airplane plus reserves you need around 2800 metres on MED/POOR

Any other carriers out there suffering the same problem, EZ?

[BOAC]

The NG 'slippery runway' figures do assume max reverse thrust, unlike the previous models which assumed idle reverse. That is going to make some difference!

[alf5071h]

The NG 'slippery runway' figures do assume max reverse thrust, ...Boeing Landing Distance Advisory Data in the QRH includes reversers for Manual and Autobrakes. This statement is made on the last slide of the Boeing presentation Airplane Deceleration on Slippery Runways – What You Should Know. (http://uk.geocities.com/[email protected]/alf5071h.htm)

This is an extremely valuable presentation explaining the peculiarities of the Boeing landing distance data.
The presentation must be read very carefully – two different uses of Mu, Certified (factored) data vs Advisory (unfactored) data, each obtained in different ways (slides 9-11). Take care with the use engineering language relating to deceleration capability (a 'value' which pilots are not aware of).
Of particular interest, note the interchange of deceleration capability between reverse and autobrake, such that in certain low friction conditions braking could be reduced as reverse meets the need for the demanded (autobrake) retardation, yet in similar conditions, brakes and reverse may not be sufficient to meet the required deceleration at all (slides 28-30).
A conclusion as a non 737 operator could be that autobrake should not be used on contaminated runways; this is hidden in the small print in the advisory data on slides 12–13 (FAA 737 FCOM).

Thus it would also appear prudent to hold thrust reverse in reserve for any misjudgment of conditions or miscalculation of the scheduled landing distance (possible contributing factors in recent accidents).

Another consideration could be that whilst JAR/CS 25.125 appears to allow the use of reverse it has to be reliable (the difference between models), perhaps an issue arising from the Midway accident; thus the NG comes into line with older variants.
CS 25.125
(3) Means other than wheel brakes may be used if that means –
(i) Is safe and reliable;
(ii) Is used so that consistent results can be expected in service; and
(iii) Is such that exceptional skill is not required to control the aeroplane.
(f) If any device is used that depends on the operation of any engine, and if the landing distance would be noticeably increased when a landing is made with that engine inoperative, the landing distance must be determined with that engine inoperative unless the use of compensating means will result in a landing distance not more than that with each engine operating.
Overall, any change that improves safety in landing operations should be welcome – just review the large number of incidents and accidents reported this year.

[Jambo Buana]

Thats a nice presentation. So are you saying that current JAR states that operators may take relief from thrust reverse or not when landing on slippery runways? The problem I have is that we are not allowed to use advisory QRH distances for in flight planning purposes and that we have to use certified, no reverse figures at both preflight planning stage and in flight. This means an increase of approx 600 metres on a MED runway, which means we wont be going to some of our destinations anymore unless they can get a MED/GOOD action, at the very least. This is not possible (not achieved) in Northern Europe very often in my experience. Previously we did allow for "Detent Reverse" thrust whatever detent meant?
Has EASA/JAA told operators to preflight/inflight only use certified no reverse performance?

[Carmoisine]

Jambo Buana,

Could you tell me where you heard this? I am an operating crew member for the evil empire and it is a bit disappointing to have to find out about things like this on PPRuNe rather then from the company!

[BOAC]

Firstly an apology - my post should have said 'detent' reverse' not 'max' for 'slippery' and 'with or without reverse' for 'normal' surfaces. This is from the QRP.

I have always taken that to mean Detent 2, ie around 70% N1.

Alf - the slides are lovely, but not much help in the air. I assume, Jambo, that you now have to carry and use the 'certified' tables rather than the QRP? As you say, you will be having 'fun' this winter.

[alf5071h]

So are you saying that current JAR states that operators may take relief from thrust reverse or not when landing on slippery runways?Jambo, the regulation CS25 deals with aircraft certification, thus aircraft manufacturers (not operators) can apply for landing distance credit in their certified data. I do not know what the JAA 737 landing data is based on, but slide 9 suggest that reverse thrust is not included in Boeing certified data, but it is (at some undisclosed value) in the advisory data. No wonder that Boeing operators report some confusion.
It may be possible for national authorities to give operators credit for reverse thrust in ‘certificated’ operations, but I cannot give an example.

I suggest that the JAR approach in requiring certified data for contaminated runway operations is very sensible; this provides a safety margin for which recent incidents indicate is a necessity. Furthermore the problems of terminology, such as the ill defined Boeing ‘Slippery’, add confusion to contaminated runway operations and could increase risk; many of these issues are presented in Managing the Threats and Errors during Approach and Landing. (www.flightsafety.org/ppt/managing_threat.ppt)

... the slides are lovely, but not much help in the air.This (Boeing slide 13) is a critical point; the advisory data is based on different set of assumptions from the certification standard, thus it requires careful consideration. Since this data is more likely to be used in flight, possibly in time critical situations, then any failure to recall the differences and to carefully consider the consequences could easily result in misjudgment of braking capability on less than ideal runway surfaces. See the advice in the speakers’ notes in Slides 6/13 of Managing the Threats and Errors during Approach and Landing ref UK CAA AIC 11/98: - see all of the speakers notes for a timely pre-winter safety revision.

The bottom line for Jambo or anyone else ‘having fun’ this winter is to recall that There is no overall accepted certification / operational correlation between mu meters and airplanes - Managing the Threats and Errors during Approach and Landing slide 26 and Attempts to land on contaminated runways involve considerable risk and should be avoided whenever possible - UK CAA AIC 11/98.

Perhaps the final thought is for all of us is not to ask “can we undertake this operation”, but "should we be conducting this operation".

[Jambo Buana]

Detent is a nice grey area isnt it! I know the main reason for providing advisory distance is for the emergency situation, and that is good info to have if youre in a spot of bother. The JAA basically accept the testing and certification that Boeing does to certify for the Feds.

Carmoisine, the latest perf preamble, which is also on crewdock, Nov 8th 06, has a bunch of new items in it. Missed app climb gradient capability is now in there for example. This should have been rolled out in the winter ops roadshow in my opinion. I think there are a few people who dont know about this yet!!!

[Carmoisine]

Jambo Buana , I didn't know, and I doubt anyone would unless they went trawling through the performance documents (Trouble sleeping anyone! :} :bored: ) .

We had mandatory read memo about Varigs financial difficulties but we didn't even get a memo for this. Sums it up all really. Sorry for the thread hijack!