ETOPS question

[loewy]

Hi all !

I have been a very frequent flyer for years (both business and leisure) with over 110 segments per year, mostly within Europe. I also hold private pilot licence and am a knowledgeable aviation enthousiast who reads most publications, including Flight International. I have alsways been very relaxed about flying an never had any serious mis-hap neither when flying commercial, nor private.

Only recently, I have started to have some strange thoughts... and questions :confused:

I read everywhere - including in these excellent PPRuNe forums - that when an engine fails, be it with or without fire, the first thing the crew does is to request landing permission. Often, one reads that the engine failure could have had significant consequences if a rapid landing hadn't been possible.

This means that, should this happen over the Atlantic, being sometimes several hours away from an alternate, an engine failure could potentially have catastrophic consequences. I am familiar with the ETOPS regulations.

I understand that my concerns are rather theoretical and that the risk is very low but I guess what I am looking for is some reassurance from you professionals that this is an event that can REALLY be managed at FL370 and poses little threat to the crew and passengers. I have just found myself a little uneasy in recent Transatlantic flights aboard 330s or 767s ...

Thanks for your replies and ... good landings,

L

[simfly]

loewy,

ETOPS, as you may already be aware, refers to twin engined aircraft. An ETOPS certified aircraft should be able to fly a certain range in the event of an engine failure, hence the extended range they are allowed to fly from land. Now, if say, a four engined aircraft had at worst case, an engine fire, it may be further away from land, so it would take even longer to reach a runway. Factors, such as engine reliability etc are taken into consideration when certifying an aircraft for ETOPS, so best thing to do when flying over the pond is just not think about it :cool:

[Bealzebub]

An amateur answer and not really correct. It has nothing to do with how far an aircraft "should be able to fly". The aircraft will be able to fly on one engine until it has no more fuel. I will attempt to simplify the philosophy.

When an engine fails in flight the crew will follow specific drills to shut down that engine and configure the aircraft for the remainder of the flight. Given the lack of redundancy a diversion will be planned to an adequate and suitable airport. Adequacy is defined as an airport that is satisfactory in respect of its runways, facilities, landing aids etc. Suitability is defined as the weather conditions at that airport at the anticipated time of use.

The introduction of large long range twin engine aircraft opened up flight operations into areas that had previously been largely the preserve of 3 & 4 engine aircraft. To cater for the fact that these aircraft would be flying to regions where they would be at extended range from adequate airports, rules and proceedures were adopted by various countries regulatory agancies to allow such operations. An "extended range" operation exists when any portion of the flight puts the aircraft more than 1 hours (still air)single engine flying time from an adequate airport.

These operations became known as ETOPS. In order to qualify for such operations the aircraft, airline and crew were subject to increased levels of equipment,reliability, maintainance requirements, crew certification and operating experience. Various levels of ETOP authorization exist that allow a qualified aircraft to be more than 1 hours single engine flying time from an adequate airport. "120 minutes", "180 minutes", etc.
It is important to remember that engine reliabilty is a very important factor in ETOPS authorisation, however it is by no means the only one. Given the astonishing reliability of these modern engines a failure is extremely rare. The other engine is perfectly cabable of flying the aircraft albeit at a reduced altitude and speed without any particular time constraint. Good practice would always dictate that in the event of a degradation to one primary system ( as in this case) the aircraft would divert. However the philosophy of ETOPS is to accept that the risk of extending the time for a diversion places the aircraft at a minimum level of additional risk. To help compensate for this extra time element, there will be supplementary requirements for such things as additional electrical generation systems etc.

You should also remember that an engine failure in a remote part of the aircrafts operating area is not the only event that can give rise to diversion scenarios. For example a pressurisation failure would require any aircraft ( no matter how many engines it had) to descend to an altitude of 10,000 feet or less in as short a time as possible. An aircraft might then be 3 hours from a suitable diversion with a very high fuel consumption ( especially so in a 3 or 4 engine aircraft). In fact it is this scenario that usually is the most critical consideration at the fuel planning stage of an ETOPS ( or Long range) flight.

As you can see there is a lot to consider of which an engine problem is only one factor. The loss of one engine will always result in a diversion, but given the requirements for ETOPS certification, that diversion time can be extended. From time to time engine failures do happen (thats why there are at least 2), but nevertheless it is so rare an occurence, that the majority of pilots these days can probably expect to get through their entire careers without experiencing one outside of the simulator.

So yes this event would pose no threat to the safety of your flight at FL370. It would not give rise to any catastrophic consequences. It can be managed easily and safely and you should rest assured that your next ETOPS flight is in fact subject to even higher standards of dispatch reliabilty than might be the case in a non-ETOPS flight.

[loewy]

The quality (and swiftness) of your comprehensive response is what makes these forums so exciting and valuable, Bealzebub. Thank you.

[strikerA320]

Beazlebub,


That's a complete ETOPS logic explanation. ;)






StrikerA320

[PAXboy]

loewy, the only detail I can add is this. When servicing an ETOPS a/c, I understand that each engine must be serviced by a different team of engineers. Should one person/the team make an error it is possible that they might repeat the error on the second engine, so this must be obviated.

You will find that RR, GE, IAS etc. all publish details of the length of service without failure of their various donkeys. The magazines have 'news' items that such-and-such an engine was on the wing for that many thousands of hours without failure and these may also help to reassure you.

I reckon that engine power and reliability is such that we shall not see any more tri-motors in commercial airliners (prop or jet), only twins and quads.

[lomapaseo]

I read everywhere - including in these excellent PPRuNe forums - that when an engine fails, be it with or without fire, the first thing the crew does is to request landing permission. Often, one reads that the engine failure could have had significant consequences if a rapid landing hadn't been possible.

All the replies above seem to be on the mark, however I would like to add my understanding in response to the quoted area above.

The first thing the crew does is to secure the engine based on symptoms. Quite often that would only result in pulling back to idle to remove the symptoms (at least that leaves the hydraulics and generator for that engine still up and running).

Even with an engine shutdown the crew still decides on landing at an airport of their choosing, quite often this is not a diversion unless of course they are down to only one engine which is the case with ETOPS (Twin Operations) vs EROPS (Extended Range Operations)

Comments, corections welcomed.

[loewy]

Once again, thanks to all for these very informative responses. Great input !

I guess the concern remains a major event (like engine fire) that requires rapid landing... However, as very well pointed out above, i) this is a very remote probability and ii) this impacts twin ETOPS as much as quad operations.

Thanks again to all,

L

[swh]

loewy,

Flying in an ETOPS aircraft can also be thought of being safer than some of the 3/4 engine brothers.....

3/4 engine aircraft always have more engines, however they do not need to meet the requirements for additional fire protection and oyxgen that an ETOPS aircraft has.

For example a 747 may have a 30 minutes fire suppression system installed in the cargo bay, where as a 767ER may have a 180 minute system in it to meet the ETOPS requirements.

Boeing and Airbus are both pushing for LROPS, a set of standards for all long range operations regardless of the number of engines.

ETOPS aircraft normally have better trend monitoring of the whole aircraft, not just the engines, which most ETOPS operators have noticed has actually reduced their maintenance bills and increased dispatch relaibility. So some airlines are going ETOPS manitenance even on non-ETOPS aircraft, as the cost benifit is justified.