Stand by for High Thrust engine failures

[Max Pointers]

The Media are reporting that Virgin and others are towing their aircraft to the runway rather than running the engines,at LGW, if this is true, and the media do have a knack of getting it wrong, then stand by for some high thrust engine failures on cold soaked engines if the powerplants internal temperatures are not allowed to reach a reasonable level before applying take off thrust.
This smacks of PR from the offices rather than commonsense from those that will have their backsides strapped to a potential management inspired problem.
So read up on your engine failure checklists and climb segment speeds guys.

[JackOffallTrades]

Sound like a complete load of journo B*&&"$$$!! Sir!

I've done a few trips from LGW lately and used engine power from push back off stand till the runway. So has everyone else I've seen.

[wiccan]

Virgin and "Others" have mooted a "push and tow" to the holding point before Engine Start.
"Could" be a "good" Idea......:D
bb

[JackOffallTrades]

Why?

You'll save a very small amount of fuel. If you need to sit at the hold for a long time..... Shut the engines down again.

[Dan Winterland]

I seem to remember many years ago that Monarch came up with the scheme of not starting the No2 (upper) engine of their DC10 until prior to take off. The desisted after a couple of very expensive engine replacements. Can anyone confirm this?

[Tommy Tipee]

I don't know about the Monarch case, but there was a popular urban legend that one of Sir Freddies finest DC10s, having been cleared for take off after taxiing on two, noticed a distinct lack of action on No.2 when applying the power.
Rapidly exited the runway with red faces, and joined the back of the queue with colourful exchange of views between Captain and F/E as to whose job it was to ensure all engines were running before take off!

[teleport]

This was announced Sir Richard in Sept.
http://news.bbc.co.uk/1/hi/business/5383908.stm

[neil armstrong]

AA used to shut down the NR2 on the 727 at busy airports (DFW) most of the times i jumpseated with them.
They would start them all up and then when it was clear there would be a que ,shut the center down till they where close to the holding point

Neil

[Flightman]

A trial with one VIR 744 was planned for yesterday. Not sure if it happened though.

[Danny]

The concept has some validity, especially at airports where queuing for departure without gate holding can use up significant amounts of fuel. It is not unusual to to use over 2 tonnes of fuel in a B747 at some very busy airports from engine start to take-off. At the moment it is only being tested at a few airports.

The BBC report on the trial at LGW can be watched here: http://news.bbc.co.uk/1/hi/help/3681938.stm

As the report says, the fuel saving is only small, when compared to the total amount used on a flight but as with all savings, if there are enough of them then it all adds up. Work it out for yourself. If every departing aircraft from LGW could save an average of just 200kg of fuel every day using a starting grid method then multiply that by the days in a year and then multiply that by every similar busy international airport and so on.

Max Pointers, whilst we are all very quick to criticise the media for getting it wrong because they don't research their stories, you could at least have googled for a bit more detail on the story before applying your own unresearched comments. The aircraft are not towed to the runway. They are towed to a point nearer the runway before starting their engines. No one has said they will start engines and then apply take-off thrust within seconds of firing them up. Do you know the minimum time after engine start before take-off thrust can be applied?

No doubt there will be other issues that will need to be resolved with the starting grid concept. For example, what if there are many aircraft at the grid? Will there be a dedicated ground engineer that will hook up to intercom on each aircraft for the start up sequence? Will all crew be happy to start without a ground engineer on intercom or outside to give hand signals? What if an aircraft at the head of the grid develops a technical problem during or after engine start? Will there be a tug standing by to tow the aircraft off the grid back to agate or a remote stand? Will there be room to manoeuvre a large aircraft with a tech problem without disrupting runway ops?

The concept is a good one, especially in today's age of cost cutting and environmental protection. However, until airports are re-designed with a properly planned 'starting grid' and the logistics are ironed out, I think it will remain just a trial. At least Virgin Atlantic are taking the first steps and providing a lead that others will follow.

[Duckbill Platypus]

It's all very well for someone like SRB to publicise the efforts his airline is making to cut costs by saving fuel and at the same time save the planet from unnecessary engine exhaust emissions. Unfortunately, there will always be someone else who will scupper the best laid plans because they are not going to benefit financially. Take BAA, the airport operator for example.

A few weeks ago, I was arrivign on to stand at BAA Thiefrow in my four engined MegaJet. It was one of those new stands at T3 with the automatic guidance that nags you when you stray off the centreline by more than a few millimetres and counts down the distance to go by giving you a fright as it changes from metres to 10ths of a metre for the last few, making it appear as though the moster is accellerating! Anyway, with about 10 feet to go (3 metres for you Europhiles) the contraption threw a wobbler and announced "ID FAIL"... "STOP".

There we were, a few metres to go until on to stand after arriving on time after a 7 hour sector across the Atlantic with our backside not protruding enough to cause a problem for aircraft needing to pass behind (if only it had caused an obstruction then the following might have been resolved much quicker). On the MegaJet we can shut down one of the four engines during taxi but as we weren't hooked up to a tug we had to keep three running.

We called ground control to advise them of our predicament and could they send a marshaller to get us on to stand. Unfortunately, it took 25 minutes for a marshaller to arrive and guide us for the last 10 feet. We tried to get our ops to find a tug but they said it would take at least ten times as long as finding a marshaller.

So, after saving several hudred kilos of fuel from the plog by audacious level changing en route and fortuitously not having to hold into Thiefrow and having our stand available on arrival we then burnt over one ton of fuel waiting for a BAA marshaller because of a shift change that was due just after we reported the failure of the stand gudance system.

It would seem as though BAA are able to solve a problem that involves their profitability such as anything to do with operating their retail shopping mall in minimum time. However, when it comes to having the necessary staff to solve problems that occur on the operational side of their airport, wasting a ton of fuel and p!ssing off a whole load of arriving passengers (they don't spend anything near as much as departing passengers do at the shopping mall) then it's a different story.

The starting grid concept is a good one but is more than likely to be scuppered early on as it doesn't involve retail opportunities for the airport operators. 'Nuff said. :ugh:

[Bus429]

I don't know if Monarch had a policy of starting G-DMCA's #2 just prior to take-off (why would they?) but I remember from bitter experience that the #2 always gave the most problems. Took ages to find the problem with its reverser - an intermittent pressure switch connection.:ugh:

[Georgeablelovehowindia]

It was standard procedure on the Monarch DC-10 to start all three on the push-back. The only time I recollect doing the delayed start procedure was in the sim.

It just so happens that I was the captain on the first No. 2 engine failure, which happened well into the climbout (approaching FL100). I can attest that when a big fan engine fails catastrophically, it goes with the biggest bang that you don't want to be sitting (relatively) close to! I was one of the three people furthest away from it, of course. Pity the rear cabin crew, who had just been released, and were standing right underneath when it went. "Yippee - Barbados, here we come!" and next second your ears are ringing and you're bouncing helplessly around the galley like a ping-pong ball.
(A graphic account at the subsequent CRM 'wash-up'.)

I think that it was to pay due attention to engine warm-up times that we started all three. Also, we had two ex-Laker flight engineers, who never told us about the attempted two-engine takeoff, so possibly fictitious?

[BusyB]

My concerns about this idea is what extra delays will apply to the aircraft that don't do it and are taxiing behind it!!:confused:

[howflytrg]

Time to start expanding stand 125 at LGW then. East, West, North South. Any starting grid will eventually reap havok on the operation of a busy airfield, especially during the mid-morning rush with the heavies starting up. Absorbing un-planned delays onstand burning APU fuel to run aircon and gens is going to become a common theme during these periods of the day. But then again they are anyway. :}

[Max Pointers]

I did not mean to ruffle Danny's feathers but I do actually know the recommended minimum warm up times for large fan engines, there are many reasons for this, and if he or anyone else want to know the facts then the Powerplant manufacturers have Reps that are readily available to talk to at all large airports in this Country.
Some of the more astute Companys actually print this advice in their Flight Crew manuals.

[PAXboy]

Max ... and if he or anyone else want to know the facts ...Actually, I think that Danny knows the facts. After all, he has been on PPruNe for some time now. Have you read his profile?

[Max Pointers]

How could you avoid his profile!!!

[Flightman]

It's all very well for someone like SRB to publicise the efforts his airline is making to cut costs by saving fuel and at the same time save the planet from unnecessary engine exhaust emissions. Unfortunately, there will always be someone else who will scupper the best laid plans because they are not going to benefit financially. Take BAA, the airport operator for example.
A few weeks ago, I was arrivign on to stand at BAA Thiefrow in my four engined MegaJet. It was one of those new stands at T3 with the automatic guidance that nags you when you stray off the centreline by more than a few millimetres and counts down the distance to go by giving you a fright as it changes from metres to 10ths of a metre for the last few, making it appear as though the moster is accellerating! Anyway, with about 10 feet to go (3 metres for you Europhiles) the contraption threw a wobbler and announced "ID FAIL"... "STOP".
I believe ICAO have mandated these automatic guidance system as the default system for stand guidance? Can't pin that one at BAA's door.
There we were, a few metres to go until on to stand after arriving on time after a 7 hour sector across the Atlantic with our backside not protruding enough to cause a problem for aircraft needing to pass behind (if only it had caused an obstruction then the following might have been resolved much quicker). On the MegaJet we can shut down one of the four engines during taxi but as we weren't hooked up to a tug we had to keep three running.
So the system went u/s. Ever had an aircraft part malfunction?
We called ground control to advise them of our predicament and could they send a marshaller to get us on to stand. Unfortunately, it took 25 minutes for a marshaller to arrive and guide us for the last 10 feet. We tried to get our ops to find a tug but they said it would take at least ten times as long as finding a marshaller.
So BAA, even during a shift change, can get someone to you in 25 minutes. Your own OPS would have taken 10x times that. And your problem is?
So, after saving several hudred kilos of fuel from the plog by audacious level changing en route and fortuitously not having to hold into Thiefrow and having our stand available on arrival we then burnt over one ton of fuel waiting for a BAA marshaller because of a shift change that was due just after we reported the failure of the stand gudance system.
And when are marshallers supposed to change shifts? Do you think they have crystal balls?
It would seem as though BAA are able to solve a problem that involves their profitability such as anything to do with operating their retail shopping mall in minimum time. However, when it comes to having the necessary staff to solve problems that occur on the operational side of their airport, wasting a ton of fuel and p!ssing off a whole load of arriving passengers (they don't spend anything near as much as departing passengers do at the shopping mall) then it's a different story.
The starting grid concept is a good one but is more than likely to be scuppered early on as it doesn't involve retail opportunities for the airport operators. 'Nuff said. :ugh:
Having been party to one of the initials meetings, sorry, you're wrong.

[BusyB]

Came into LHR pax on wednesday. As an example of how well BAA run LHR, of 5 travelators between my arrival gate and the bus station, 3 were NOT working. Matches the efficiency of crew security!!:ugh:

[Sheep fancier]

The Media are reporting that Virgin and others are towing their aircraft to the runway rather than running the engines,at LGW, if this is true, and the media do have a knack of getting it wrong, then stand by for some high thrust engine failures on cold soaked engines if the powerplants internal temperatures are not allowed to reach a reasonable level before applying take off thrust.
This smacks of PR from the offices rather than commonsense from those that will have their backsides strapped to a potential management inspired problem.
So read up on your engine failure checklists and climb segment speeds guys.

Sat for a couple of hours last year at Norfolk International Airport in Virginia and every Delta MD80 that passed was only just starting the 2nd engine as it neared the holding point.

SF

[MrBernoulli]

A trial with one VIR 744 was planned for yesterday. Not sure if it happened though.

I left LHR yesterday p.m. (Wed 13 Dec) for a trip to India and remember hearing ground ATC asking a Virgin callsign if he was part of the towing trial. Reply was in the affirmative but he sounded somewhat sheepish?!

I have some concerns about this idea of towing aircraft to somewhere nearer the rwy. Will a tug be able to cope in wet/icy conditions? Can a tug haul a large transport aircraft across an in-use rwy faster than the aircraft can move itself? I don't bloody think so!

[Wunwing]

I operated in and out of the old Hong Kong airport for about 25 years. If you were on one of the outer bays near the entrance to the RWY it was not unusual to be on the RWY within 3 mins of completing last engine start. Never had a problem with engines, biggest problem was fuel tank sampling and finishing all the check lists.

[quazz]

Just from a passenger comfort point of view, the aircraft that I fly has a less than efficient air conditioning system if the engines are not running. After the summer we've just had I think the pax and crew would probably have died long before our start and take off clearence.

[dash6]

Brilliant idea. I've been thinking about a scheme like this for ages. Wish I'd patented it! Why not? How many aircraft moving on apron at any one time? Thats the number of lift and tow tugs you need. Tug stays with A/C and releases it only when cleared by ATC poss 2/3 mins beforeanticipated T/O clearance. If as well as AC power,tugs could supply external air, think how much fuel burn and noise could be avoided. This of course =less pollution.Think how much the tree huggers will love it! Once the tug has finished at the holding point, it can go to the upwind end, and tow in an arriving A/C.Only losers the tug guys,who will be too busy to finish the crossword.Once this really gets going I envisage a new generation of high speed tug,which will accelerate the A/C to Vr whilst the crew are starting the engines:) :) All for it!

[mini]

From a logistical viewpoint its probably viable, contingent on the required resources being made available - this is where the number crunching will come into play.

Factor in the "soft" (!) issue aspects such as negotiating new role training, responsibilities and the inevitable financial claims that will be associated with crewing the ground ops end of it and you'll no doubt end up with a compromise that will go t*ts up when a tech issue or similar happens.

Sorry to be cynical...:sad:

[Max Pointers]

In order to increase the thrust of modern large fans the tip clearances on turbine and compressor blades have been reduced to the minimum possible, therefore it is important for the core temperatures of the rotating and stationary parts to be reasonably stabilised before you start rotating it in the region of 14000 rpm or more. What we used to do with the old P&Ws and RRs is immaterial. When I opened this thread it was about a PR exercise that Virgin had made sure the media blurted out on most TV channels in the South, so that we all knew that it was not only SRBs beard that was going green, and to gain even more public exposure, on the cheap.

If we take all of this fuel saving to the logical conclusion that this thinking opens the door to, then Culdrose and St Mawgan should be the departure airports for all US flghts after the aircraft have been towed along the M4 and M5 it gets a bit tricky past Exeter though.
So you all take care now.

[Bus429]

It was standard procedure on the Monarch DC-10 to start all three on the push-back. The only time I recollect doing the delayed start procedure was in the sim.
It just so happens that I was the captain on the first No. 2 engine failure, which happened well into the climbout (approaching FL100). I can attest that when a big fan engine fails catastrophically, it goes with the biggest bang that you don't want to be sitting (relatively) close to! I was one of the three people furthest away from it, of course. Pity the rear cabin crew, who had just been released, and were standing right underneath when it went. "Yippee - Barbados, here we come!" and next second your ears are ringing and you're bouncing helplessly around the galley like a ping-pong ball.
(A graphic account at the subsequent CRM 'wash-up'.)
I think that it was to pay due attention to engine warm-up times that we started all three. Also, we had two ex-Laker flight engineers, who never told us about the attempted two-engine takeoff, so possibly fictitious?
George,
Do you have one of G-DMCA's slats in your garden?

[fiftyfour]

The airbus 320 has 5 mins limit from cold start(ie not a short turn round) to full power at take-off.
At major airports like LGW LHR it takes 3 to 10 mins to get to the runway from he stand (depnds on which one).
So if ATC and the slot system could be sorted out, we wouldn't have the long delays that force Virgin into this stunt.
Saw the Virgin 747 try this at LGW a few days ago. The aircraft gets towed to the area at the beginning of 26R between Bravo and Charlie. After start it joins the queue at Alpha 2 or Alpha 3. Didn't look like much of a saving to me and just blocks the area near the runway. It probably releases the stand earlier to an incoming aircraft, so that's a saving of kinds.

[TimV]

Folks,

I regularly pax on bmi A320/19s out of LHR and it seems common practice to shut down one engine after landing for the sometimes lengthy drive to the gate. Rather than fill up all the taxi ways with tugs would it be possible to taxi on one engine on the way to the runway as well? Start up point for the remaining engine could be as you come near to the end of the take-off queue. Can 747s and A340s taxi on 2 engines - if so they could fire up their remaining engines in a similar way. The fuel savings would obviously be less than every aircraft being towed on taxi, but logistically might this be a better compromise?

Tim

[Georgeablelovehowindia]

Bus 429: No, I don't have ANY part of 'CA, only the fond memories!

However, if you care to go with your metal detector to an area approx. 20 miles south-west of Midhurst, and find any H.P. IGV bolt, the H.P. compressor, and the turbine assembly off a General Electric CF6-50C2B then I would be delighted to make your acquaintance! ;)

Regarding taxying in on one engine: We tried that on the 737 and the 'Powers That Be' decided that what we gained in fuel, we lost in scrubbed nosewheel tyres.

[late developer]

I saw the first BBC report on this and I don't like the idea. I can't believe it is a safe thing to have introduced, and not just because of the questionnable mechanical systems aspects pointed out by Max.

To me it is very obviously NOT a very valid attempt at being environmentally friendly. It is pure PR following on from RB's big "I'm donating everything to save the world" speech a little while back.

I would have thought Virgin had had more than their fair share of engine problems over the years without pushing the limits of engine management like this.

Does this also mean that they will be carrying even less fuel than before?

How does this big change affect likely Human Performance and Limitations in their cockpits prior to take off?

Like others, I can't quite see how the tug angles stack up either.

Safety before Fuel Savings please, and don't muck about.

[CHIVILCOY]

What will the environmentalists have to say when all that lovely turf has to get ripped up to make way for the acres of tarmac needed to extend the holding areas.

[Swedish Steve]

What we used to do with the old P&Ws and RRs is immaterial.

Well when I was a sprog in BEA, someone came out with the bright idea of shutting down nbr 3 engine after landing to save fuel. Must have been 1970!! About 6 months later the exercise was stopped after we noticed that 80% of the Trident engine failures were Nbr 3 posn.

[Max Pointers]

Yes because the temperatures also have to stabilise again, particularly after reverse thrust has been applied otherwise the 'cold' section cools down quicker and binds on the turbine tips I am told, though Saudia had the same problems with OATs of 42 centigrade.

[HR200]

Why?

You'll save a very small amount of fuel. If you need to sit at the hold for a long time..... Shut the engines down again.


Wrong, at ground level, where the air is denser, a jet or turbine engine uses a fair bit of fuel even at idol power.

Also, a jet engines life is partly measured on number of start-ups, so unneccesary start-ups and shut downs are to be avoided.

Being towed to the holding point sounds like a very good idea in thoery, but I dont think it will be very practical.

[RatherBeFlying]

Once this really gets going I envisage a new generation of high speed tug,which will accelerate the A/C to Vr whilst the crew are starting the enginesSome glider folks are talking up the fuel saving advantages of winches. Will need a longer runway for a jet transport and something like the steam catapults used by the USN:}

[NWT]

Some important points being missed here. Many flights land at airports like LHR and hold for a long time for a gate to become free, if the aircraft on the gate is ready, but just waiting for ATC then it could be towed to the remote holding area whle waiting for the clearance. Provided the engines have the correct warm up time then there is no problem. I seem to remember the practice of towing of to a remote and leaving the crew to strt themselves when ready was very common practice at LGW North terminal not long after it started. Many airlines already have the proceedure of shuting down one engine during taxi -in (provided cool down time is OK). The benefits of towing a/c to departure points will be much more at airports like JFK where a taxi time of an hour or more is normal. I think a lot more effort needs to be put into matching a/c departure times with ATC/runway slots so the extended holding on taxiways is minimised. And yes the BAA could do a lot more to aid the situation; like have a beter level of serviability of jetties, ground electrics, aircon units on the stands that actually work and cool the aircraft! and so on....

[BEagle]

And when the first of Sir Dicky B's jets gets stuck when the towbar gets snagged....or the shear pin goes?

Or tries to get airborne with a nose lock still in place?

Penny wise, pound foolish, to my jaundiced eye!

[Gonzo]

if the aircraft on the gate is ready, but just waiting for ATC then it could be towed to the remote holding area whle waiting for the clearance.


But if it's ATC holding you on stand due to airfield delay, the fact you're waiting for tow to the grid will be immaterial. You're still a movement from our point of view. It won't get you off the gate any quicker.

Now, if you're talking about remote holding for a slot delay, we've been doing that at Heathrow for years.

[Earthmover]

The place to do something like this is surely Schiphol. I believe 18R/36L is, at the longest routeing, about 7km from the terminal. Somebody correct me if I'm wrong, but I believe this runway, located near the town of Haarlem, was constructed in order to appease the 'Greens' ... so now we burn thousands of tonnes of extra fuel (releasing more dreaded CO2) every year in order to ensure we are all more environmentally friendly.

Jeez :ugh:

[Tako Yaki]

Guess none of these geniuses thought about the amount of diesel pollution the extra push-back tractors will be pushing out at each airfield in order to save a drop or two of Jet A.

[Self Loading Freight]

The logical conclusion is to have everything slotted up like Scalextric, with a San Francisco-style cable drive pulling stuff along. ATC would control the lot like a giant train set, and with a special arrangement on parallel runways you could use the energy from a landing a/c to accelerate one taking off. Have a ramp at the end, like a carrier, and off you go.

R

[barit1]

...Somebody correct me if I'm wrong, but I believe this runway, located near the town of Haarlem, was constructed in order to appease the 'Greens' ... so now we burn thousands of tonnes of extra fuel (releasing more dreaded CO2) every year in order to ensure we are all more environmentally friendly.

Jeez :ugh:

Why, it's our old friend, the law of unintended consequences! :cool:

[Continuous Ignition]

If I recall correctly, United Airlines tried this plan of towing their B744's out toward the departure end of the active at KORD for their China flights several years ago and Boeing nearly had a cow. Seems the Nose Gear isn't designed to be towed for that distance at Max weights. Can anyone confirm this?

[barit1]

Getting to the heart of the matter--High Thrust Engine Failures:

When an engine is shut down for a short period, the casings cool and shrink on the hot rotors, perhaps causing a temporary interference between blades and seals. Restarting in this condition can carve up the clearances, causing high EGT and fuel burn, but is seldom the direct cause of engine failure. Letting the engine cool fully (several hours) means the clearances will re-normalize, although it probably takes only 1/2 hr. for the interference to disappear.

But in between these extremes, another phenomenon happens: convection air currents within the engine carcass tend to warp or "bow" the rotors and stators. Hot air rises, so the upper half of the engine is slightly hotter and expanded, while the lower half cools and shrinks faster. When the engine is restarted in this condition, the bowed rotor being unbalanced will shake for a while until the temperatures equalize. If you're taxiing at idle for several minutes, the vibration settles down. BUT--going to high power with a bowed rotor can be damaging.

So - towing an aircraft out to the runway should not, in itself, cause engine failures, so long as enough warmup time is available to clear the vibs from the bowed rotor.

Here endeth the lesson.

[18-Wheeler]

So - towing an aircraft out to the runway should not, in itself, cause engine failures, so long as enough warmup time is available to clear the vibs from the bowed rotor.
Here endeth the lesson.


Agreed - I used to fly a 747 Classic out of Nadi in Fiji. The taxi from the terminal to the end of the runway is very short, and we made very sure the last engine had at least three minutes to warm up. In the decade or two of operating 747's, I don't recall of hearing of that company having an engine failure along those lines.

[PAXboy]

Continuous IgnitionSeems the Nose Gear isn't designed to be towed for that distance at Max weights. Can anyone confirm this?This has been discussed and, IIRC, dismissed. I have looked for the original thread on this topic (this being the second or third) and cannot find it. (It probably went to JB after folks started making observations about the man who started VAA.)

As I recall, this was strongly discounted as being a problem. This was based on Boeing info and the consideration of the weight and stress that the n/g takes during normal taxi-out. It would be interesting to know the down force on the n/g.

Talking of strength of the n/g strut: when that A320 landed on the West Coast of USA recentley with the tyres rotated to almost 90 degrees - the photographs showed that the strut was intact, only the tyres and hub were damaged. If a strut can take that amount of dragging along the ground at landing speed - it would seem possible for it to withstand extended towing at low speed?

I sit to be corrected.

[Max Pointers]

Barit1 has got it right.
Many first users of the Deceased X and the Tripestar had a checklist for Bowed Rotor Syndrome, ie failure of the engine to rotate after the starter motor is engaged, however I notice in a recent purchasers Flight Crew Manual of one of these "classic" aircraft all mention of the problem had been removed, so I guess many years and various owners down the line, somebody has been filleting the manuals to save a tree.

[Max Shutterspeed]

Guess none of these geniuses thought about the amount of diesel pollution the extra push-back tractors will be pushing out at each airfield in order to save a drop or two of Jet A.

Or the wages and strike demands of the tug jockeys! Just imagine how important they're going to feel.

Neill W