Some questions on flighing

[anamorph]

Hi,
I'm new to this forum, and the reason I am posting is this:
I flew for the first time on 28th May this year, and I have to say,
at the time I sat down on the plane a panic attack came on, and I very nearly had to get off. I calmed myself down, but got nervous again as I felt the 737 taxi (quite bumpy) however as son as the pilot put the foot down to take off I was OK, and looking out the window was amazing. Ive flown twice since then,
with less nervousness (except for a bumpy landing at Edinburgh)
But, me being me, I find that knowing about things takes away the fear. So, here I go with some questions......
First, as a pilot, if any of you thought the conditions were unsuitable, would you refuse to fly to a particular airport, or divert?
Second, as a whole, how confident are you in your aircraft before you take off? ie would you fly with dodgy instruments?

Third, how dangerous is turbulence?

I realise these questions may seem stupid, but, I hope you understand my reasons for asking them. I will almost certainly post more questions, but for now I hope to read some honest answers...

jim

[wing_nut1]

hey Jim,

Cant say i am a comercial pilot but i work as ground staff and communicate with pilots a lot and know roughly what goes on.

Firstly, if they thought the weather was un-suitable for landing they would not risk lives and try and land. They have safe limits which they are allowed to go to but if they cant at that point they 'go-around' and will divert to another location.(quite frequently happens where i work:mad: )

Secondly, regarding instruments, they are all efficent have i think have double if not triple the sets needed so if one did fail they is plenty of back ups. (quite rare for one to fail) if they can spot a dodgy instrument on the ground they wont hesitate to get an engineer out to have a look at it.

Thirdly the question regarding turbulance. If memory servers me correctly certainly larger planes like 737's and 747's and built to withstand forces larger that mother nature can throw at them so certainly 'average' turbulance its not a problem (just makes the passengers feel queezy):hmm:

I hope the above is some use and if you have any more questions dont hesitate to private message me or add a reply and i will gladly assist as much as possible

Wing Nut:ok:

[Tinstaafl]

This is a very broadbrush answer:

There are defined limits to what sort of weather conditions are acceptable for landing & take-off. If the weather is below the required conditions then the flight won't depart or attempt to land although some weather conditions can make it quite acceptable to make several approaches. An approach doesn't guarantee a landing at the end of it and there is always the option to discontinue the approach. Fuel to go to somewhere else where a landing is assured is nearly always required to be on board.

Remember it's the pilot's neck too. Most of us value our necks a lot. I work on the principle that getting my neck there safely also gets my passenger's neck there too. Damned if I'm going to risk my neck for someone's bloody holiday.

The minimum required instruments for a given flight are set by the country's aviation authority in association with the aircraft manufacturer. Many of them must have redundancy ie there be alternatives. Others are 'nice to have' not 'need to have'. Some flights require different instruments to others eg a particular navigation aid.

If the intrument is required for the flight to occur then the flight doesn't leave without it. If it's a 'nice to have' then there may be an option in the aviation/manufacturer/operator's rules for the flight to leave with it not working. There's nearly always additional requirements that must be met in that case.

The aircraft is built & certified to withstand the sorts of forces that will leave most passengers forced uncomfortably (and scarily) into their seats, lunged against their seatbelts or vomiting in the aisle. Operating rules and limitations are set to near as dammit guarantee the a/c is maintained withing those certified limits. As a further safety measure the airframe is constructed so that it would typically have to experience at least 50% more load before any damage.

But like I said: Most passengers will be chundering all over themselves long before the a/c bats it's aluminium eyelid.

[anamorph]

Thanks for that, guys. Ive never experienced bad turbulence, just about 2 seconds worth that felt like driving on a bumpy road.
It's when I hear other people saying things like "10 minutes before we landed the plane dropped like a stone for about a thousand feet" That I must say, scares me, but , I don't fancy vomiting in the aisles either....

I have always thought "Well if it was THAT dngerous I don't think the pilots would be doing the job...."

I think part of it comes from : I hate not seeing where I'm going, so I do all I can to get a window seat, usually in the middle of the plane. The problem is, then you see the engine wobbling about (even if you can't feel it) - that happened at 36,000 feet when I was returning from Nice last month, and in fact I didn't even think clouds went that high: it was like a thick murk, the pilot kept the seatbelt lights on for 45 mins while he avoided what he called "rather large clouds, just in case" Once the plane got into clearer skies, the wobbling stopped. It's just that they do look a bit fragile.... although I know they are immensely strong..
The thing is a lot of the worries I have are silly, but I still like to know about them to try and store it in my mind...

My favourite parts in flying are: takeoff (exhileration) : looking at the cloud tops and land (gorgeous) : and braking on the runway (relief the plane is on the ground)

So, here are some more questions, the most ridiculous first.
I read about the centre fuel tank combustion when empty on the 737.or.uk site, quite worrying. Since (i assume) the budget (and maybe for that matter other) airlines don't carry much more fuel than they need for a given journey, how many UK airlines run planes with an empty tank? (Please be honest on this)

If a plane has to (if it can) land at a faster speed than usual due to weather, how much braking ability does it have in reserve over normal?

On a percentage basis (low visibility excepted), how much is the balance between pilot/ATC as regards other aircraft - ie is the pilot completely ignorant of other planes, or are there other ways of knowing?

And (for now).....;) lastly, on a 737, the tyres are not inside the plane when the wheels are up. How much does this matter at 30 odd thousand feet up? Surely freezing and heating up isn't good for them? (For that matter, I also think "Stone me that plane was up in the stratosphere 20 minutes ago, now it's in boiling heat, and in another hour it'll be freezing again" I take it this is all accounted for in the designs as well?

[PAXboy]

Hi, just another pax but with about 38 years experience!! Of the questions that you pose now, some are related to the previous answer. In that, the CAA regulations cover things like braking too. If the runway is too wet or covered in ice, then the nice people at the pointy end take us somewhere else where it's clean!

As to turbulence in the air - the big difference now is that aircraft have very good weather radar. Nowadays, airlines know that pax will accept a short delay to arrival, whilst their go around the nasty clouds and not through them. This is probably why your pilot was avoiding those clouds. The last time I had really bad turbulence was in 1970 when the a/c (a Viscount) could not clear a storm and went through it at 16,000 feet. Nowadays, even when popping down from EDI to LTN, you will top 25,000 or even more. Generally speaking, the higher you go the smoother. However, some thunder clouds in the tropics can reach 45,000 and higher! That's when it is time to drive around them.

As to the wheels of the 737 not being fully enclosed - no problem. The 737 has been around in one form or another for 30 years and they have enormous experience in designing the tyres that can experience these changes in atmospheric pressure and temperature. Although many other a/c do have enclosed wheel wells, they are not heated - so the tyres get just as cold as the 737's. The tyres are designed that they will expand as the a/c climbs (basic physics!) and then contract as it descends.

By the way, welcome to Pprune! :D

[Jerricho]

Hey Jim,

I'll try and answer the ATC bit of your question. You may hear in the media that ATC are trying to stuff as many jets on their 4 km long piece of concrete, while trying to throw the same number in the air. But, as you probably know, we have very strict "minimum separation" requirements we have to adhere to.

Your question about aircraft landing at a faster speed is a good one. While the pilot is ultimately responsible for his/her aircraft, ATC will try not to put them in situations where this may not be the case. As I said above, out separation is a minimum, and can be increased for what ever reason. For instance, if we have really bad visibility, "Low Visibility Procedures" are put into force, meaning we increase the spacing on final approach. This ensures the landing jet can land and get off the runway well before the next lander gets there (there is also a consideration here of our ILS - instrument landing system.......I can explain this if you like as well). Other times we can increase spacing on final approach is, as you asked, if it is bucketing out of the heavens and the runway is very wet (increased braking distance as you asked, but then again, Heathrow's runways are 3900m and 3600m long!), or if we have different aircraft (like Concorde) that fly faster down the final approach at a faster speed than others.

And pilots are not totally oblivious to the other aircraft about them. You may have heard of TCAS - Traffic Conflict Avoidance System, which acts a little like our radars on the ground, but isn't used in the came way. Also, it isn't hard to see other jets about you out the window (especially in a hold!). Sometimes visual separation between aircraft can be used if it's going to make things run a little quicker.

[Rollingthunder]

On the subject of fully enclosed wheel wells on the 737 - most do have them, a smaller number do not.

Love the flighing btw.:O

[CR2]

Jim, just a point on the "wobbling". An aircraft structure is flexible - just imagine if it wasn't, you'd have bits and pieces snapping off.
Try and look at the wings on a B747 when it takes off; they are so full of fuel that they bend upwards (known as dihedral).
If I remember correctly, Concorde expands 13 inches in length during supersonic cruise. This from the heat generated on the fuselage due to friction with the atmosphere.

[maxman]

The next time you hit turbulence and are worried, have a look at the flight crew, if they are not worried, you shouldn't be, they've been there, done that.
A humble pax opinion.:ok:

[radeng]

The captain has a switch to deal with turbulence - the seat belt sign. Generally, it works like this: Turbulence starts, captain puts on seat belt sign, makes announcement, a number of passengers (frequently, I regret to say, from my observation, Americans) ignore it, cabin crew get them seated, and then the turbulence goes away.

I believe the technical term is 'Sod's Law'.