Can I help you

Purrrrrfect.

Jimmie76

Down Boy!

WHBM

The Power Transfer Unit (PTU), source of the sound, has been described by others. There are two, duplicated, hydraulic systems around the aircraft, driven by the engines, and when the pressure in one falls relative to the other, such as when one engine is shut down, the PTU springs (or barks) into action to pressurise one system from the other. There seem to more questions about this than just about any other aircraft noise.

As I understand it, it is a BMI procedure to taxi A320s on one engine where BA does it on two, which will explain hearing it at different times. I do recall reading a while ago that Airbus, after umpteen complaints from operators about the sound, had finally come up with a modification to deal with the noise, but don't know if it was only an option, or only installed from a certain airframe number.

If you have a spare half hour and want the low-down on the PTU operation, it's here.

http://www.chipsplace.com/helpful/Airbus/Hydraulics.htm

ColdWalker

A question that came up at the social last night: How are runways named? The numbers refer to the direction they point in, but could 08 also be called 26 when landing at the 'wrong' end? Why is 09R at LHR on the right and not the left - ie is there a convention as to which direction you are looking when deciding if it is 09R and not 09L? Is the other runway 27R if you are coming from the east, if you see what I mean? If there were a third runway in the same direction would it be 09middling-diddling?

1010101

09R is also 27L, depending on which way you face in relation to North.

If there are more than 2 runways of the same orientation they change the number by 1 i think or sometimes use C as a designator.

Airprox

It is the runway magnetic heading rounded to the nearest 10 degrees and expressed as 2 digits, so you know roughly in which direction the runway points.

09L and 27R at Heathrow are indeed exactly the same piece of asphalt. If you were stood on the 27L threshold (by T4) looking down the length of the runway towwards the T5 end, you would be facing a magnetic heading of 271 degrees, hence this runway would be called 27. If you were stood on the other end looking back you would be facing a heading of 091 degrees. There are 2 of them that are parallel, and they can't both be called runway 27, so when looking at the runways in the direction they are numbered, so heading west the left hand one is called 27L and right hand one 27R. Of course when you are looking along the runways from the othe end, they are then called 09L and 09R.


If you have 3 parallel (for example at Frankfurt), then you call them L C and R. If you have 4 parallel (at several US airports including Los Angeles, Atlanta, Orlando and eventually Chicago) then you normally use 2 sets of numbers each, with a left and right. LAX for example has 4 parallel runways, numbered 24L, 24R, 25L and 25R (in the westerly direction), even though they all have the same heading of 250 degrees.

In areas where the difference between magnetic north and true north (called the declination) are very large, such as nearer to the poles, it becomes pointless using magnetic heading as a reference for the runway direction. In this case True north is used as the reference, and the runway number has a T added, for example runway 02T.

As the magnetic heading of a runway changes over time, eventually they have to be renumbered. Heathrow's runways that are now 09R/27L and 09L/27R were once upon a time runways 10R/28L and 10L/28R. In more recent years Stansted's runway has changed from 05/23 to 04/22 and Manchester have changed theirs from 06L/24R, 06R/24L to 05s and 23s.

ColdWalker

OK Airpox, I think I have got it. So the Northern of the two runways at LHR would alternatively be called 27R or 09L. The logic being when travelling West, the Northern runway would be aligned to apx. 27(0) degrees and would be the right one of the two. Correct?

Airprox

Precisely. 27R when you are using it in a westerly direction, 09L in the easterly direction. So when you tell a crew they will be landing 27L, that one piece of information is enough to specify which bit of tarmac is being talked about and from which end it is being used.

Runways can normally be used from either end, and thus have a different number at each end that are 180 degrees apart. There are occasions though when for some reason you cannot use a runway in one direction, and thus it becomes a one-way runway (try saying that quickly!) and therefore will only have a designation for that end and not the other way.

Heathrow has had many runways over the decades, the last of which to be withdrawn from use was the old 05/23 (previously 05R/23L) which ran from the north-east corner of the airfield down to the bottom of T4. AFAIK, and hopefully Scott or HeathrowTower will be along soon to confirm, the 05 end was withdrawn quite some time earlier, so that at the end of it's life this was a one-way runway operating as runway 23 only.

FenLandK

I saw some crew yesterday, while waiting for my much delayed flight home from OSL, that had "Union Crew" bag tags. Now, my question isn't so much about that (I'm not wanting to get drawn into discussions on Union/Non-Union), but it did make me think - do BA have a policy on bag tagging? I mean I can see advantages and disadvantages of having a bag tagged as "Crew" (with or without "Union"), but would BA consider this a crew security risk in any way? I don't recall seeing many crew bags marked in this way, and it may be because these ones looked very new and bright white.

ColdWalker

One for the cabin crew I think. The starboard door on the upper deck was out of action on my flight today. There was a big notice on it saying "no exit". I asked the crew about it after the briefing, just so I was absolutely clear where to go if push came to shove. She explained the stairs are the primary exit, which I knew, but that the doors are only used in a ditching. I thought (from our Cranebank course) that the upper doors were not used in a ditching as the upper slides affected the free release of the lower slides as rafts.

Did I misunderstand? What the actual usage of the upper doors?

Separately it was interesting that the plane was OK to be airworthy (or whatever the proper term is) with a door u/s.

Can I help you

BA no longer provides crew with luggage tags and these new unions one are permitted.

Can I help you

The primary evacuation route from the upper deck in a land evacuation is by the upper deck doors, during the safety briefing the one usable door should have been pointed out, the pre-landing announcement should also include a reminder of this.
The primary evacuation route from the upper deck in a ditching is from one of the main deck doors.

ColdWalker

thanks I did think the ditching comment was odd. I wouldn't fancy exiting into the sea from 40' unless I had to - a rather easy way to end up drifting away from the rafts! Glad to know I was not being dumb on the course ^

The one u/s door wasn't mentioned in the briefing, but they weren't the most switched on crew on the u/d to be honest. In fact the cross check was only done by one person on both take off and landing, which I can't say is the end of the world, but it does rather make a mockery of doing a cross check.

Can I help you

I not sure what mode the unusable door would have been left in, which might explain what you perceived as the lack the cross checking.

Littlegirl

We are required to label our bags with our name and staff number. BA used to provide us with tags for this but now for some unknown reason they don't.

Many crew have had Union tags, for as long as I can remember, but they were of a darker and probably less noticible colour. During the Idustrial action some unusual baggage tags started to be used, highlighting that people had taken industrial action, and BA decided to ban all non standard and union tags. However since the agreement and the restarting of talks between BA and the union, BA have agreed that crew can now use official union tags.