Help needed!!

[JerryMaguire]

Hey guys, help needed for this questions as I prepare for the interview.

1) Where are the commercial plane research/testing facilities for Boeing and Airbus? I’ve always thought that it is Seattle (State of Washington, United States) and Toulouse (France) respectively. Can anyone confirm that?

2) Aircraft Engines – Broadly speaking, there’s Piston and Turbine Engines. However, the confusion for me starts when I read abt Turbo Jet, Turbo Prop and Turbo Fan. I’ve tend to associate Prop planes with Piston engines. Henceforth, does turbo prop and turbo fan planes have swept wings just like the jets? I’ve read on comparison btw the Piston Propeller (with straight wings, can generate more life, more sensitive to speed changes, less power and hence lower altitude) vs Jet turbine planes (with Swept wings and less lift but more power and hence able to achieve greater altitude) but am not sure if turbo jet = jet turbine planes?

3) Can someone give a typical climb/descent profile for a jet plane with attention paid to the descend altitude with respect to range to airstrip, Vertical descend rate, IAS/TAS, pitch of the aircraft. Also, is there a difference in this during VFR and IFR? Does this apply across the commercial jet families (Airbuses and Boeings)? Obviously the profile depends on the overall weight of the plane (lighter plane can descend later) but I was just wondering based on design on aerodynamics of the planes if any one aircraft currently has the advantage over another.

Thanks so much!

[Teroc]

Lots of questions Jerry. Im sure i'll get shot down on some of my answers but here goes.

1. Yep. Seattle for Boeing and Toulouse for Airbus. These are their main production plants, their HQ's, and a lot of testing is done here.

2. OK here goes. Lets keep it simple.....you can spend your life being pedantic about this !!....

Turbo-Jet= The very first type of jet engine. All the air entering the front is compressed, combusted and sent out the back passing through a turbine stage on its way. The turbine stage at the back is connected to the front compressor. The turbine spinning at the back drives the compressor at the front which sucks more air in and so on etc etc etc.

http://www.allstar.fiu.edu/aero/flight64.htm

Turbo-fan = Much more air than a turbo-jet is taken in at the front large fan section. Most of this air (75 to 80 %) is ducted around the power section, i.e. doesnt get burnt, and is mixed with the remaining 20% combusted air in the exhaust. This engine produces a lot more thrust than a turbo-jet for the same fuel burnt, is more fuel efficient, and is quieter.

http://www.allstar.fiu.edu/aero/flight65.htm


Turbo-prop= Think of a turbo-jet engine. Now instead of the turbine being connected to a compressor stage its connected to a propeller. Air comes in the main air-intake, gets compressed, burnt, sent off to the turbine stage which starts spinning which in turn drives the prop at the front from which thrust is generated.

http://www.allstar.fiu.edu/aero/flight66.htm


3. Again simple everyday stuff. Multiply your altitude, in thousands, by 3 for the distance you should be at for a 3° glideslope. Example..
a. I'm at 30,000 feet
b. Drop the thousands = 30
c. 30 x 3 = 90
Answer - I should start descent at 90 miles from the airport.

8000 feet = 8
8 x 3 = 24
Start descent 24 nm from airport.

3000 feet = 3
3 x 3 = 9
Start descent 9 nm from airport

What should be your rate of descent ?
Roughly 5 Times your groundspeed.... so groundspeed is 150 kts 150 kts x 5 = 750 feet per minute descent rate.

Approach speed - Varies with weight and aircraft type. Typical boeing 737 landing speed.. about 135 kts.

Pitch of the aircraft - Again varies with aircraft type. Aircraft like a B737 its about + 4° to + 2° nose up. But many variations, like weight, flap config, is it a single engine approach ? change this so its hard to say.

http://www.b737.org.uk/pilotnotes.htm


Hope this answers some of your questions and you find the links useful. I can hear them building the gallows for me already ..... :ouch:

[Dusty_B]

Jerry,

Also, is there a difference in this during VFR and IFR?

Nope.

Obviously the profile depends on the overall weight of the plane (lighter plane can descend later)

This isn't true at all. Weight has nothing to do with the ability to descend. As Teroc explains, we tend to use "rules of thumb" that are based on a standard descent gradient (3 miles for every thousand feet), and from that a rate of descent required based on your speed (5xGroundspeed).
The caviat to this is on fast unpressurised aircraft, where a high rate of descent could be too uncomfortable for the passengers (ie, 5x200kts = 1000fpm). Pressurised aircraft has "cabin" descent rates not in excess of 300fpm - Big difference!

[JerryMaguire]

Hey Teroc, appreciate the kind links you've attached. I've gone through it, beyond the pasted links and found them really useful. :o)

There are 3 major engine manufacturers in the market: Pratt and Whitney, Rolls Royce and General Electric, (now there's even an Engine Alliance btw PnW and GE) The aviation world is really amazing! :o) Have gone through the websites and I'm convinced that these are the turbo fan engines.

Question: It seems that GE 90 is the world record holder with 120,000 Ibs of thrust. The rest of RR Trents and even GE 7000 engines average produce thrust of only abt 90,000 Ibs of thrust. Does this high thrust value makes it more attractive? I din think so since the A380, a much larger plane compared to the B777 (which GE 90 is meant for) only needs a Trent 900 to keep it going. I guess it's fuel efficiency airliners are concerned with but seriously how reliable are the SFCs given and how much difference these really means? Perhaps it's the price which makes all the difference? Which brings me to asking if anyone has a link to price guide for these engines?

Hey Dusty B, I read somewhere that there is a maximum speed restriction during descent due to the Landing Distance Available (LDA) and hence there is a need for a heavier aircraft to make a shallower descent. ie a lighter aircraft can descent faster and later. Not sure if that is true though.

[Teroc]

Glad you found the links useful Jerry.

I dont know of any website where pricing is specified for engines. At the end of the day the airlines care about the bottom line..money.
If theres a choice of say 2 engines from diff companies, which are both approved for the same airframe it'll all come down to running costs.

These Running costs, maintenance schedules, breakdown ratios , fuel efficiency etc etc all come into the equation but how the bean-counters ultimately decide on this i have no idea.

There is a max speed of 250 kts below 10,000 feet which is an atc legal limit and obviously LDA is involved in the calculation to determine if you can make it into the airport in the first place but ive never come across larger aircraft making shallow descents purely due to LDA. I can see where youre coming from but the differences in weight between normal commercial aircraft be they 747's or dash 8's wouldnt require any deviation from
the usual 3 ° glideslope.

Remember as well if the airport only has a 3° ILS on the field thats all youre getting !! You cant play around with it (ahem !! ) . Assuming youre doing an IR approach Youre coming down
that 3 ° pipe whether you like it or not.. :E

[JerryMaguire]

Yeah, running costs. I was just reading that boeing was complaining on the big discounts Airbus was giving to airliners on it's A320s, so much so that this has undercut into the demand for their 737s. Anyhow, I was just wondering if anyone knows generally which engine is typically most costly to maintain.

ILS, I've read a lot abt it. Are the errors significant? I've read that it gathers errors like False guide slopes, Phantom Signals and Backcourse approaches.

Have anyone heard abt the MLS? Microwave landing system. I've read abt that and it seems that the advantage of this is that one can make a curved approach as compared to the typical ILS where one can only make a designated 3 degree glideslope as you've correctly pointed out.

Is there like a website that actually lists airports with ILS. My assumption would be that the major hubs shld all be ILS equipped?

Further, I've read that it is impractical to keep the aircraft pressurized at sea level pressure. (14.7 psi). Any idea what pressure we'r talking abt?