questions
Thread Starter
Joined: May 2000
Posts: 326
Likes: 1
From: UK mainly
questions
Hello I wondered if the boffins could help me out I have a few trivia questions, (preparing for that lucky break in aviation at the moment!)
1, Please could someone explain EPR?
2, What is a "super stall" ? (don't say superman stalling?!)
3,How does Vmca vary with Cof G?
4,what are the adv/disadvantages of INS
5,CAT how does it occur?
6,what make the features of the b777 unique from other aircraft?
Thankyou so much for answering these questions whilst sometimes PRruners sometimes whine on other forums this forum certainly is worth it's weight in gold!
regards to all
1, Please could someone explain EPR?
2, What is a "super stall" ? (don't say superman stalling?!)
3,How does Vmca vary with Cof G?
4,what are the adv/disadvantages of INS
5,CAT how does it occur?
6,what make the features of the b777 unique from other aircraft?
Thankyou so much for answering these questions whilst sometimes PRruners sometimes whine on other forums this forum certainly is worth it's weight in gold!
regards to all
Fleet Manager
Joined: Apr 2001
Aviation Qualifications: ATPL
Posts: 7,447
Likes: 310
From: various places .....
I'm sure that, over the next few days, you will get lots of answers ... but, first, try a search of the forum for the keywords and you will be ahead of the action .... for instance, I just ran a search on "EPR" and came up with 40-odd threads ...
PPRuNeaholic
Joined: Jun 2000
Posts: 3,255
Likes: 0
From: Cairns FNQ
I've had a go at writing answers for all those questions but quickly realised that it would be one helluva long post that could well take several days online to complete! So here's the challenge... anyone reckon they can fully answer all the points in the same post, taking less than a day to write it? 
I'd have to agree with John_T that searching PPRuNe topics will produce answers to most, if not all the questions.
I'd have to agree with John_T that searching PPRuNe topics will produce answers to most, if not all the questions.
Joined: Aug 1998
Aviation Qualifications: ATPL
Posts: 6,623
Likes: 847
From: Ex-pat Aussie in the UK
The quick answers then ... 
1, Please could someone explain EPR?
EPR stands for Engine Pressure Ratio, it is a measure of the amount of thrust an engine is producing and is the pressure of the flow at the back of the engine, divided by the pressure of the flow at the front.
2, What is a "super stall" ? (don't say superman stalling?!)
A stall is when the aircraft's wings are hitting the air at to much of an angle, and the air cannot flow smoothly over the top of the wing. "Super Stall", and sometimes "Locked-in Stall" are rather out-dated terms for what is more commonly known as a "Deep stall", or when the angle of attack increases so that the disturbed air is flowing back over a "T-tail" elevator, reducing the control in pitch to the point where recovery (pitching down) is difficult or impossible.
3,How does Vmca vary with Cof G?
Vmca is defined under a set of given conditions, one of which is "the most unfavourable CofG", so the strictly correct answer here is "it doesn't vary". A rear CofG reduces the moment arm of the rudder, reducing the effectiveness in yaw, thus as the GofG moves rearward, speed must be higher to maintain control.
4,what are the adv/disadvantages of INS
Over what? Advantage - you know where you are, Disadvantage - if it breakes, you don't know where you are any more!
5,CAT how does it occur?
Different air masses, moving at different velocities, create turbulence at the boundary between the masses where they "rub up against each other".
6,what make the features of the b777 unique from other aircraft?
The B777 isn't particularly unique! It's is the world's largest twin jet, it was the first aircraft to use digital to design and electronically pre-assemble the entire airplane, first aircraft ot gain 180 min ETOPS on initial certification, the flight deck includes a Ground Maneuver Camera System, the landing gear is the largest ever incorporated into a commercial airplane etc, etc.
1, Please could someone explain EPR?
EPR stands for Engine Pressure Ratio, it is a measure of the amount of thrust an engine is producing and is the pressure of the flow at the back of the engine, divided by the pressure of the flow at the front.
2, What is a "super stall" ? (don't say superman stalling?!)
A stall is when the aircraft's wings are hitting the air at to much of an angle, and the air cannot flow smoothly over the top of the wing. "Super Stall", and sometimes "Locked-in Stall" are rather out-dated terms for what is more commonly known as a "Deep stall", or when the angle of attack increases so that the disturbed air is flowing back over a "T-tail" elevator, reducing the control in pitch to the point where recovery (pitching down) is difficult or impossible.
3,How does Vmca vary with Cof G?
Vmca is defined under a set of given conditions, one of which is "the most unfavourable CofG", so the strictly correct answer here is "it doesn't vary". A rear CofG reduces the moment arm of the rudder, reducing the effectiveness in yaw, thus as the GofG moves rearward, speed must be higher to maintain control.
4,what are the adv/disadvantages of INS
Over what? Advantage - you know where you are, Disadvantage - if it breakes, you don't know where you are any more!
5,CAT how does it occur?
Different air masses, moving at different velocities, create turbulence at the boundary between the masses where they "rub up against each other".
6,what make the features of the b777 unique from other aircraft?
The B777 isn't particularly unique! It's is the world's largest twin jet, it was the first aircraft to use digital to design and electronically pre-assemble the entire airplane, first aircraft ot gain 180 min ETOPS on initial certification, the flight deck includes a Ground Maneuver Camera System, the landing gear is the largest ever incorporated into a commercial airplane etc, etc.
