Random facts about planes..

[5150]

AVV EM said:

My contribution -

The air you breathe in whilst on board an aircraft is actually 'bleed air' from the compressor stage of the turbine engine.

You could have mentioned it's conditioned before it's let out into the cabin!

[Buzz84]

Mrs Buzz works in the aircraft industry so I've heard a few of these

Atomic12C said:

On many commercial planes there is a triangle symbol above some of the windows (internal).
This is to denote the leading edge of the wing and also the trailing edge of the wing.

I was told that these triangle symbols were to tell the cabin crew which window has the best view of the front and back of the engines, So if there was a problem the crew knew exactly which window to go to if asked to by the captain. This can even be done on the sleigh by the cabin crew passing or stopping to "check" on the passengers there

Nanook said:

texaxile said:

They used to transport spare /replacement engines bolted to the wing (underneath). I have been on a Gulf Air Tristar back in the 70's which had this, 2 engines on 1 wing and 1 on the other.

Is it the A380 that has a spare compartment for stiffs during the flight?.

Some 747s can carry an extra engine inboard on the port wing.

Virgin Galactic have got one of Virgin Atlantic's retired 747s and plan to launch satellite carrying rockets from that hard point.

For "stiffs" I believe these compartments are optional and can be spec'd by the airlines - usually reserved for longer routes

[pushthebutton]

Nanook said:

Not on the 737 I worked on? Unless you're right, and the engineer changing the bottles over for new ones, that I was helping, was wrong?

Sounds like a 100/200 and not a 400.

http://www.b737.org.uk/emergency_equipment.htm#Pas...

300s onwards have chemically generated oxygen for the passengers.

[Atomic12C]

Buzz84 said:

I was told that these triangle symbols were to tell the cabin crew which window has the best view of the front and back of the engines, So if there was a problem the crew knew exactly which window to go to if asked to by the captain. This can even be done on the sleigh by the cabin crew passing or stopping to "check" on the passengers there

Yes basically for the same thing.
The leading edge of the wing is so that cabin crew can check for wing slat or engine problems.
The trailing edge of the wing for cabin crew to check for flap/aileron issues or engine problems.
But essentially the cabin crew can quickly note the location of the wing in order to quickly assess views of any issues relating to the wing or engines.

[pushthebutton]

AVV EM said:

My contribution -

The air you breathe in whilst on board an aircraft is actually 'bleed air' from the compressor stage of the turbine engine.

Except the 787 (and maybe other types I don't know about) which uses electrically driven compressors.

[yellowjack]

Buzz84 said:

Mrs Buzz works in the aircraft industry so I've heard a few of these

Atomic12C said:

On many commercial planes there is a triangle symbol above some of the windows (internal).
This is to denote the leading edge of the wing and also the trailing edge of the wing.

I was told that these triangle symbols were to tell the cabin crew which window has the best view of the front and back of the engines, So if there was a problem the crew knew exactly which window to go to if asked to by the captain. This can even be done on the sleigh by the cabin crew passing or stopping to "check" on the passengers there

[Zetec-S]

yellowjack said:

Buzz84 said:

Mrs Buzz works in the aircraft industry so I've heard a few of these

Atomic12C said:

On many commercial planes there is a triangle symbol above some of the windows (internal).
This is to denote the leading edge of the wing and also the trailing edge of the wing.

I was told that these triangle symbols were to tell the cabin crew which window has the best view of the front and back of the engines, So if there was a problem the crew knew exactly which window to go to if asked to by the captain. This can even be done on the sleigh by the cabin crew passing or stopping to "check" on the passengers there

[Buzz84]

yellowjack said:

Buzz84 said:

Mrs Buzz works in the aircraft industry so I've heard a few of these

Atomic12C said:

On many commercial planes there is a triangle symbol above some of the windows (internal).
This is to denote the leading edge of the wing and also the trailing edge of the wing.

I was told that these triangle symbols were to tell the cabin crew which window has the best view of the front and back of the engines, So if there was a problem the crew knew exactly which window to go to if asked to by the captain. This can even be done on the sleigh by the cabin crew passing or stopping to "check" on the passengers there

Well what do you think Santa does in the summer season, in flight engine inspections!

[RizzoTheRat]

Most big aircraft have a Ram Air Turbine that can be deployed to generate electrical or hydraulic power in the event of engine failure. The RAT on the A380 is has blades over 5 feet in diameter.

The development aircraft in the Typhoon programme didn't have RATs which contributed to the crash of the Spanish one when he lost both engines.

[Atomic12C]

The start procedure for a jet engine is not just pressing a button and off you go...
Step 1 - use an external compressed air source to start spinning the blades/internal compression system. (or use plane's own auxiliary power unit if available)
Step 2 - wait until a specific minimum revolution velocity has been reached.
Step 3 - then introduce fuel and wait for ignition
Step 4 - then allow the engine to become self powered
Step 5 - allow the engine to stabalize.
Step 6 - air pressure from engine one can then be channeled to engine two for its own start up procedure.

[Dr Jekyll]

Atomic12C said:

The start procedure for a jet engine is not just pressing a button and off you go...
Step 1 - use an external compressed air source to start spinning the blades/internal compression system. (or use plane's own auxiliary power unit if available)
Step 2 - wait until a specific minimum revolution velocity has been reached.
Step 3 - then introduce fuel and wait for ignition
Step 4 - then allow the engine to become self powered
Step 5 - allow the engine to stabalize.
Step 6 - air pressure from engine one can then be channeled to engine two for its own start up procedure.

How does that compare with a turboprop? And what is the dreaded 'hot start' phenomenon?

[IforB]

Nanook said:

Not on the 737 I worked on? Unless you're right, and the engineer changing the bottles over for new ones, that I was helping, was wrong?

You have Oxygen bottles for crew and chemical generators for passengers.

Boxygen bottles and proper masks mean that pressurised oxygen can be breathed whereas a chemical generator and mask is just releasing oxygen for you to breathe. It'll help keep you alive for a bit, but won't help you function, whereas for crew it's more important for them to have more opportunity to keep compos mentis

[Mabbs9]

I'm surprised they fitted a RAT to the 380. Most 4 engine types tend not to need them.

Regarding the engine starts, happily they're mostly computer controlled. Just occasionally a manual start is require. My previous type we started two engines at a time. Great system, it would detect problems in the start sequence, abort the start, blow out excess unburnt fuel, check EGT has dropped below 100' then try a second time, usual using both ignition systems as the most common cause of a failed start would be an ignitor fault.

[BrettMRC]

The B52 and the Space Shuttle share the same onboard computer system. (Good ol' IBM)

You can get a 747 to go near/through the sound barrier, but its not recommended:
https://en.wikipedia.org/wiki/China_Airlines_Fligh...

[TVR1]

Atomic12C said:

But essentially the cabin crew can quickly note the location of the wing in order to quickly assess views of any issues relating to the wing or engines.

It would worry me though, if the Cabin Crew didn't know where the wings are. Being that they are those long, stickyout things attached to the metal tubes thing they're currently flying in.

And what happens if they can't find the wings? That's what I want to know?

[Eric Mc]

BrettMRC said:

The B52 and the Space Shuttle share the same onboard computer system. (Good ol' IBM)

You can get a 747 to go near/through the sound barrier, but its not recommended:
https://en.wikipedia.org/wiki/China_Airlines_Fligh...

You can get a DC-8 to actually go THROUGH the sound barrier.

I would guess that the computers on the B-52 were installed after they were selected for Space Shuttle orbiters as orginally, there would have been very little computing power in B-52 systems. Indeed, versions of the IBM AP-101 have been used in a range of US aircraft.

https://en.wikipedia.org/wiki/IBM_System/4_Pi



In fact, the Space Shuttle Orbiter had FIVE computers.

[bad company]

Even new aircraft still have an ashtray in the toilets although smoking is obviously banned.

Apparently it's to stop anybody throwing cigarette ends into the wast paper container causing a fire risk.

[IforB]

Dr Jekyll said:

Atomic12C said:

The start procedure for a jet engine is not just pressing a button and off you go...
Step 1 - use an external compressed air source to start spinning the blades/internal compression system. (or use plane's own auxiliary power unit if available)
Step 2 - wait until a specific minimum revolution velocity has been reached.
Step 3 - then introduce fuel and wait for ignition
Step 4 - then allow the engine to become self powered
Step 5 - allow the engine to stabalize.
Step 6 - air pressure from engine one can then be channeled to engine two for its own start up procedure.

How does that compare with a turboprop? And what is the dreaded 'hot start' phenomenon?

Something like a PT-6 turboprop engine uses an electrical starter /generator unit to get the turbine spinning and then you introduce fuel to the spark and get the thing self sustaining.

A Hot start is where the ITT (Inter Turbine Temperature) breaches the limits and can seriously damage the turbine. This often happens as there isn't enough air flowing through the engine to keep the thing cool. It overheats rapidly and you have a very nasty problem. Doing a start downwind can contribute to this sometimes as can introducing fuel too early. Modern FADEC systems help limit this issue (Full Authority Digital Engine Control) but in ye olden days (and it's still good practice now) you'd watch the gauges like a hawk with your hand on the fuel valve to shut it down fast if it started to get hot.

[RizzoTheRat]

BrettMRC said:

You can get a 747 to go near/through the sound barrier, but its not recommended:
https://en.wikipedia.org/wiki/China_Airlines_Fligh...

There was also an Evergreen Airlines cargo 747-100 that had an autopilot malfunction that lead to a 90 degree roll before the crew noticed, Mach 0.98 and it lost 10,000 feet in the recovery
https://aviation-safety.net/wikibase/wiki.php?id=1...


Re startup, can the APU be started electronically or does that need external air too?


The EJ200 engine in the Typhoon has an annular combustor with multiple fuel injectors (I can't remember how many). The early trials rigs didn't have a decent fuel balancing system so it was possible to back the fuel far enough so that it was only burning on the bottom few injectors (in a combustor rig, don't know if it would have been generating enough power to keep a whole engine going). This meant there was a lot of unburned fuel coming out of the back. So if you were living in the Filton area in 2001 and your washing ended up smelling of kerosene, sorry.

[5150]

Dr Jekyll said:

How does that compare with a turboprop? And what is the dreaded 'hot start' phenomenon?

Exactly the same - a turboprop is jet-engined too.

Hot Start - pretty much what it says on the tin. Normally down to slow motoring of the engine, incorrect fuel metering, or insufficient air flow through the engine (or a combination of these). Most modern aircraft will automatically abort for a hot start as it monitors the temp and the trend upwards towards the maximum prescribed limit for start. Old(er) jet engines, require it to be manually recognised and shut down, otherwise things get a bit messy / lot of paperwork.