767 "Gimli Glider" Questions

[MMEMatty]

I just watched the movie of the "Gimli Glider" on C5 UKTV earlier today. For those that dont know, its basically the story of a Boeing 767 that runs out of fuel in Canada, the Captain, FO and a passenger who is also a pilot have to try and land it at a disused airfield. Stirring stuff, and it is based on a true story. Now my questions are thus:

At one stage the captain turns and says "Good job the cabin pressurisation is working, we dont want the oxygen masks to drop and panic the passengers"-why is the pressurisation working? from my (admittedly limited) knowledge, the pressurisation comes from the engines. The engines stop, so does the pressurisation. Does it run off the little drop-down turbine they use?

When the engines fail, so do the electrics (and therefore the transponder) , untill the drop-down generator thingie comes into action, and ATC naturally get a little upset that the aircraft drops off their screen. Fair enough, i understan why. ATC then switch to primary radar which sends out the radar beam and sweeps the sky looking for the aircraft, like a lighthouse, however it takes several minutes for the aircrafts blip to come up-why? is this just Hollywood suspense or did this really happen? if so why?

Thirdly, did the Captain really say "God bless you...and the boeing aircraft company of Seattle" when the Generator came into play at the nick of time? sounds a bit melodramatic to me.

Finally, Has anyone ever tried the "Run out of fuel" scenario on the 767 sim? Would be interested to know if you like "every one of the original pilots to try it" crashed. Honest answers please ;)


Sorry for going on for so long, no doubt i could condense what ive said, but ive tried to place some of the questions in a context for those that havnt seen the film. quite whether ive done a good job is up to you.

Thankyou for your patience and i look forward to your replies


Matty

[rich49]

If your interested, get the book 'EMERGENCY Crisis on the Flight Deck' by Stanly Stewert. It is a fantstic book full of stories (about 10) like that. It also includes the 'Gimli Glider'. The book goes into a LOT more detail than the film and is also more factual, giving the full reason why the fuel ran out. It is quite a complicated set of misfortunes and misunderstandings that caused this to happen.
Anyway, your questions.
The pressurization system would indeed fail if the engines ran down and their would be a limited oxygen supply available, your right. However the pilots had already started a decent into winnepeig as they were aware of a problem. They quickly decend below 10,000ft were the pressurisation system is no longer needed for comfortable breathing oxygen. In other words, the pressurization system DID fail. It just did not matter because they were low enough.

The generator is called an RAT, or Ram Air Turbine. It provides hydraulic power to the flight controls and the instuments on the flight deck run off of a battery. The EFIS screens (those big screens in front of the pilots) in real life would go blank. The film is unrealistic here. ATC would theirfore be able to pick up a trace and did in real life. ATC never lost the aircraft. The RAT deploys when N2 (the high pressure stage of the engine) drops below a certain value, so yes, the whole 'nick of time' thing was down to hollywood.
I hope this helps. I cannot answer your last question, I am not a pilot. (yet anyway!)

BTW: Did you notice that in parts of the film that F/O Quintail had one F/O's eupelete and one captains one?
Cheers
Richard
Edited for spelling

[radar707]

From an ATC point of view, we would never lose "radar contact" with the a/c as we would still have the use of primary radar (i.e the dot without any information)
The information is provided by secondary radar (SSR), which interogates the transponder on board the a/c and provides us with various information including callsign, level, speed

[ChrisVJ]

Not sure about the " every pilot who tried it in the sim" thing but some testied it last year for real when a plane ran out of gas ( thanks to a leak) over the atalntic and put her down on an Island military base. Heavy landing, but plane recoverable. No serious injuries.

If I remember the plane was an Air Transat on a flight from Canada. No one really knew whether to hang the pilots for failing to notice the fuel loss or pin a medal on them for getting it down safe. I'm for the medal.

[ICT_SLB]

The definitive book about the incident is "Freefall" by William & Marilyn Mona Hoffer (ISBN 0-312-02919-5). Couple of points:
1. You can pressurise most jets using ram air & the cabin altitude limiters will also help retain pressurisation.
2. There are battery back-ups for the Avionics on the 767 & I beleive the RAT can also power a hydraulically-driven generator. (Sorry I don't have my 767 schematics at home).

I do know that the whole fuel system was redesigned after Gimli with particular emphasis on making sure you couldn't mix imperial (pounds) with metric (kilograms) between the Fuel Quantity Computer and the EICAS and thus inadvertantly show a "correct" fuel load when under half had been uplifted!

[FlapsOne]

Can't speak for the 767, but we practice double engine failures and glide approaches on the 737. I believe the guidlines we use came from a 767 operator.

The best glide seems to be about twice the height for miles to run. 20,000 = 40 miles, plus or minus wind factor of course.

Gear and any flap will be very late when landing on concrete assured. As to how much flap you get depends on what services are available from APU (if there's fuel left), RAT (767) etc etc.

Done it in the sim a few times and survived every one but you sure touch down fast!!!!

[dmdrewitt]

The Gimli Glider was repaired and is still in service today with Air Canada.

http://www.airliners.net/search/photo.search?regsearch=C-GAUN&distinct_entry=true

Shows a photo only last november taking off in Florida! Amazing!

Dave

[Tan]

Yep that's 604 all right; I flew that airframe many times. Many years after the incident, US ATC still used to inquire if that was "the airplane". It sure generated a lot of interest.

Both the Captain and F/O are now retired. On occasion I have the opportunity to have a pint with one or both of them on the last Tuesday of every month. By the way the F/O did retire as a 767 Captain. The Captain retired as a 747-400 skipper.

Do they ever talk about the incident? Hardly ever, although Bob still does the occasional Japanese interview.
:)

[john_tullamarine]

FlapsOne,

Interestingly, on the 732/3/4 it doesn't matter where you take gear and flaps ... comes down to profile management and a bit of judgement as to where to turn ... I've had pilots do all sorts of different configuration change schedules and get in with ease .. an interesting exercise, none the less ...

[Tan]

posted 14th January 2003 23:51
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John

In my experience with the "shuttle approach”,"double hush" whatever one what's to call them the biggest factor in achieving a successful landing is the ability of the pilot to step out of the box of SOP's and then step back in at the appropriate time. Those that couldn’t think outside the box had the most trouble. By the way there was a thread a while back dealing with this very subject.

Normally only the Captains at my airline were given the opportunity to experience this exercise and then only at the end of the session, if there was time, as it was not recognized by the licensing authority.

[john_tullamarine]

Tan,

Have to agree with your thoughts ....

The best group I have seen were ex-FJ from an Asian country during a refresher program ... they all approached the problem quite differently .... all got in (some rather more tidily than others).

The results of my own first attempt at the exercise shall remain a closely guarded secret ... no point in embarrassing myself unduly ...

[QAVION]

"At one stage the captain turns and says "Good job the cabin pressurisation is working, we dont want the oxygen masks to drop and panic the passengers"-why is the pressurisation working? from my (admittedly limited) knowledge, the pressurisation comes from the engines. The engines stop, so does the pressurisation. Does it run off the little drop-down turbine they use? "

The drop-down turbine (RAT) is only for providing hydraulics. It is activated above 80kts in the air with both engine N2's below 50%. However, the pressurisation system may have been able to maintain some sort of pressure in the cabin simply by slamming shut the outflow valve (in the absence of sufficient air coming from the aircon packs). It would be stale air, but I wouldn't be complaining. I couldn't say for sure if ram air, windmilling the engines would be able to provide sufficient pneumatic pressure to power the aircon "packs" to provide cabin air pressure. The pack valve may close at a specific level of (low) bleed air pressure like they do on certain other aircraft. Actually, I'm not even sure that the packs would operate at all without proper elec power(???).

"When the engines fail, so do the electrics (and therefore the transponder) , untill the drop-down generator thingie comes into action, and ATC naturally get a little upset that the aircraft drops off their screen."

No electrics from the RAT, unlike some aircraft. The power to operate a transponder may have come from a Hydraulic Motor Generator (some 767's have three of them, one on each hydraulic system). I'm guessing that the windmilling engines might provide sufficient power to operate 2 of the HMG's. There may have been a delay in the HMG's powering up, however: The hydraulic pressure coming from the EDP's would be less than normal and some HMG's are a little reluctant to start up, if at all, if not exercised regularly. Also, there is a sequencing of HMG's. An HMG may wait until others have failed before coming to life.

More speculation, I admit, but this scenario is certainly is great food for thought.

Regards.
Q.

[Uptrim Disable]

For a dual flameout, what glide speed (maximum Vl/d) would you use for the 737 (any version)? What about the DHC8-100/300? The OM doesn't say anything about it, but surely, Boeing and DeHavilland know which AoA (or speed) to go for?
Just curious!

[MMEMatty]

Least drag airspeed? i am just a (very) low time ppl but i would presume that would be the one to go for?

Matty

[Uptrim Disable]

Uh, yeah, but where can one find this speed? It's not in the books...

[Motormouse]

Can't say for all aircraft types,
but those I'm familiar with that have ram air, the ram air inlet is a naca inlet somewhere(usually lower fuselage),and the ducting by-passes the air-con packs.

The essence of pressurisation of course is to control the air getting out of the cabin via the outflow valves.

[QAVION]

"Can't say for all aircraft types,
but those I'm familiar with that have ram air, the ram air inlet is a naca inlet somewhere(usually lower fuselage),and the ducting by-passes the air-con packs. "

Unfortunately, there is nothing like this on a 767.... other than the Naca scoops for the aircon pack heat exchangers (However, this air doesn't go into the cabin). The bleed air from the engines which is used by the packs... and the air being sucked in by the Naca scoops doesn't mix... It's more like a car radiator (where water and air don't mix).

Regards.
Q.

[Onan the Clumsy]

When the engines fail, so do the electrics (and therefore the transponder)

I thought there was an automatic switch to the battery bus and then load shedding was activated. That would give you some power for a while. Also, doesn't the third horizon have to have it's own independent 30 minute power supply?

[QAVION]

"I thought there was an automatic switch to the battery bus and then load shedding was activated. That would give you some power for a while."

The battery provides power to only certain aircraft systems, Onan. Those that use DC power can work directly off the battery, those that require AC power require a Static Inverter which converts DC to AC. ATC is AC-powered, but is not normally one of the systems powered by the Static Inverter (for power conservation reasons).

"Also, doesn't the third horizon have to have it's own independent 30 minute power supply?"

You're probably thinking of newer generation aircraft. The design of the 767 is quite old. These NG aircraft have low power LCD Integrated Standby Flight Displays... and the dedicated battery can last up to 150 minutes (depending on battery charge). The 737NG, some Airbusses and the 747-400ER have these.

Regards.
Q.

[Notso Fantastic]

Least drag speed is usually about holding speed or very close to minimum flaps up speed, which for a 737 is 210 knots or a 747 about 240 knots. At those speeds you really have an efficient glider- a 747 can be hard to get down - unless you have run out of engines in which case it is still much too fast).

[None]

> The power to operate a transponder may have come from a Hydraulic Motor Generator (some 767's have three of them, one on each hydraulic system).

Qavion; actually some 767's have one HMG (now called HDG by the new Boeing books). The HMG comes on-line automatically (after a 10-15 second delay) with the loss of both left and right AC buses. To power the HMG the center hydraulic system's ADP (Air Demand Pump) is signaled to operate (the selector must be in Auto).

The HMG powers 7 buses. The Left (#1) transponder is powered, as is the Captain's flight instrument bus for a full EFIS compliment.

[Eckhard]

Uptrim Disable,

MMEMatty is correct when he says that min drag speed would give you best glide ratio. As to where to find it, it would be very close to best holding speed or best angle of climb speed, both of which are available from the FMC. Best hold speed is also available in the perf manual. A deviation of + or - 20kts or so would probably have little effect and I personally would shoot for about 240kts in a 737, which may be on the high side but would give better windmilling and a little more energy for turning, etc.

On a 747, I would go for 240 - 280kts, depending on weight.

[QAVION]

"Qavion; actually some 767's have one HMG (now called HDG by the new Boeing books). The HMG comes on-line automatically (after a 10-15 second delay) with the loss of both left and right AC buses. To power the HMG the center hydraulic system's ADP (Air Demand Pump) is signaled to operate (the selector must be in Auto)."

Agreed, "None"... but since there is probably insufficient bleed air in this scenerio to run an ADP, I only mentioned the 3 HMG-type 767. The windmilling engines and the EDP's are more likely, however, to provide power to the HMG's on the L & R Hydraulic systems (or have I overlooked something obvious?).

Regards.
Q.

[None]

>but since there is probably insufficient bleed air in this scenerio to run an ADP, I only mentioned the 3 HMG-type 767. The windmilling engines and the EDP's are more likely, however, to provide power to the HMG's on the L & R Hydraulic systems (or have I overlooked something obvious?).


To my knowledge, there are no 767s with 3 HMGs. For ETOPS 767s, there is one HMG (Hydraulic Motor Generator, now Hydraulic Driven Generator), powered by the ADP, which receives air from the Center Pneumatic Duct. The source of the air is whatever is pressurizing the center duct.

The electric hydraulic pumps are A.C. powered.

[QAVION]

"To my knowledge, there are no 767s with 3 HMGs."

Qantas has three on their -300's and one of their -200's. I'm sure they are not unique in this respect.

Regards.
Q.