Ask The Pilot

jb747 said:
A few different ways. Some aircraft have cooling fans built into the wheel hubs. We use conditioned air from the terminals, ducted to the hubs....where it's installed. The place we need it most is Dubai, and they've got it there.
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Is there a reason why a bucket or two of water thrown over the brakes wouldn't do the job? Or would they just crack?
 
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Just a reminder about the unique guidelines applicable to this thread:

NM said:
As this is an "ask the pilot" thread, we ask that non-pilot members refrain from answering questions that have been directed to pilots until the pilots members have had a good opportunity to answer the question (i.e. at least 7 days). Posts contrary to this request or discussions that get too far off topic may be removed or moved to a more appropriate thread or forum so we can retain order and respect in this thread.
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flychrisfly said:
Is there a reason why a bucket or two of water thrown over the brakes wouldn't do the job? Or would they just crack?
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I'm not sure the engineers would like it. Apart from the issues of warping the discs, there are issues with the bearings and the ingress of water.

With the miltary trucks I used to drive, four wheel drive (or six, depending on the type) had to always be selected when fording (water). Not for traction, but when selected, it pressurised the hubs and gearboxes to prevent the water seeping in as all the hot bits got cold very quickly. Wheel bearings don't like contaminated grease.

Speaking of wheels. And gear out. I was at Parramatta the other day (or month) when we were overflown by a (I think Etihad 777) heading west, climbing, but wheels still out. And off it went until it was out of sight. Gear down.

Could the pilots have forgotten to retract? Is there a warning system? Any other possibilities (besides tech)?
 
jb747 said:
I'd hate to think what that would do. There's a lot of thermal mass in the assembly, and they can get up as high as 700ºC.
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AVC said:
I'm not sure the engineers would like it. Apart from the issues of warping the discs, there are issues with the bearings and the ingress of water.
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This seems to imply then that there are structures in place to prevent water from a wet runway from touching the brakes on landing?
 
flychrisfly said:
This seems to imply then that there are structures in place to prevent water from a wet runway from touching the brakes on landing?
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I expect a spray, as they'll get on landing, would be instantly vapourised. A larger amount might be a problem. The brakes are contained within the wheel hubs, and aren't totally exposed. If cooling them were as easy as pouring water on them, then I doubt that they'd go to the trouble of installing cooling fans, or outlets from the terminal a/c.
 
Hi JB I am on QF 9 on 30th October MEL-LHR then on QF10 on 3rd November LHR-MEL and wondered if you were going to be driving?
 
I had planned to ask this on the Saturday night dinner for AFF8, but it completely slipped my mind.

My fiancée is a big Bill Nye fan and much less so a frequent flyer, however found out that he developed a hydraulic pressure resonance suppressor for the 747 as one of his first jobs that's still used today on the newer models.

We'll be taking a trip out to LRE next month and knowing where to look when out there would be helpful, but also knowing what the hydraulic pressure resonance suppressor was used for/why it's important would be lovely too.

Hoping you can enlighten us.
 
samh004 said:
I had planned to ask this on the Saturday night dinner for AFF8, but it completely slipped my mind.

My fiancée is a big Bill Nye fan and much less so a frequent flyer, however found out that he developed a hydraulic pressure resonance suppressor for the 747 as one of his first jobs that's still used today on the newer models.

We'll be taking a trip out to LRE next month and knowing where to look when out there would be helpful, but also knowing what the hydraulic pressure resonance suppressor was used for/why it's important would be lovely too.
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If you'd asked me, I wouldn't have been able to look it up on Google.... To be honest, I've never heard of one.

This might be a good place to look. http://www.wilkesandmclean.com/Suppressor5-20.pdf

Sounds like the sort of thing you use in your house to eliminate 'water hammer'.
 
Do you know your December schedule yet?
I'm hoping that you're flying QF9 on the 4th of December.
 
On my way to SYD this morning on a delayed 767, the crew said that they would make a high speed descend into SYD to help make up some time. Does it really make much of a difference? I would think that, as long as ATC allows, the plane would be pretty much be going as fast as it can from cruising altitude to just above 10,000 feet anyway?
 
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Awesom Andy said:
On my way to SYD this morning on a delayed 767, the crew said that they would make a high speed descend into SYD to help make up some time. Does it really make much of a difference? I would think that, as long as ATC allows, the plane would be pretty much be going as fast as it can from cruising altitude to just above 10,000 feet anyway?
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On a short sector, it makes a surprising amount of difference, especially if ATC also let you exceed 250 knots below 10,000' as well.

A standard descent is current cruise mach number, converting to an IAS of 280 knots. A high speed descent, would start at an IAS that would be about 20 knots faster than usual, and because of the IAS TAS relationship at height, that could be around 40 knots extra groundspeed. At lower levels you could still be about 60 knots faster than usual. So, over the roughly 20 minutes of a descent, you could make up about 3-4 minutes. If you're in a real hurry, you also delay the descent point, and plan on using max speed brake for the entire descent. That keeps you high for longer, and there can be another minute to be saved there, but it's uncomfortable as it involves a steeper than usual pitch attitude, and makes it hard for the cabin crew to secure the cabin.
 
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