76
votes
Accepted
What is this hatch above the cockpit of a 747?
It's an emergency escape hatch. There are inertial reels in the cockpit ceiling adjacent to the hatch to allow the cockpit crew to exit the airplane. See this link for an account of their use escaping ...
- 39.2k
58
votes
Accepted
Why does the second floor of the Boeing 747 occupy only part of the plane?
The basic design of the Boeing 747 was originally developed to for the US military's CX-HLS program for a large cargo aircraft. One of the main requirements of the program was for cargo to be loaded ...
- 71.8k
55
votes
Accepted
Is this aerodynamic braking procedure normal in a 747?
This is not a recommended procedure for landing the 747 (or any other jet airliner I know of). The FCTM (Flight Crew Training Manual) says this:
After main gear touchdown, initiate the landing roll ...
- 54.3k
47
votes
Accepted
Can the A380 ferry an extra engine, like the 747?
One of the main reasons the 747 was given the ability to ferry an engine was due to the lack of large cargo aircraft available at the time.
Don't forget the 747 was a major game changer when it came ...
- 1,067
46
votes
Accepted
Was the Space Shuttle aerodynamically neutral while piggybacking, or did the combination act like a giant biplane?
This podcast with one of the pilots answers just about every question on the shuttle carrier you could have and it's worth a full listen. But to cover the flight dynamics, I would skip to 50:33 ...
- 100k
39
votes
Was a six-engine 747 ever seriously considered by Boeing?
The "fifth engine mount" option on the 747 is not designed to handle a running engine. It was an option used only by Qantas as a means of ferrying spare engines to remote locations, where flying a ...
- 3,010
38
votes
Accepted
Was the Boeing 747 designed to be supersonic?
No. The Boeing 747 was not designed for supersonic flight, though during testing, it was pushed quite close to the sonic speed:
Tom Cole, a spokesman at Boeing Commercial Airplane Co., said original ...
- 100k
38
votes
What could explain the fact that during 1976-80, I used to hear commercial jets make sonic booms while flying overhead?
Note that 747's and other jumbo jets operating out of Bradley could not have produced sonic booms because they do not fly above the speed of sound (they only do 500 to 550 MPH at high altitude cruise) ...
- 20.7k
36
votes
Are there any Boeing 747 still flying for commercial use?
Quite a few, actually.
British Airways is the largest operator of B747-400 and flies a number of routes:
Where does the Boeing 747-400 fly?
The aircraft operates on a variety of routes, ...
- 100k
33
votes
Accepted
Does a Boeing 747-830 exist and if it does, is there any difference to a 747-8 (748)
Until 2016 Boeing included customer codes into the aircraft model names. Your example 747-830 decodes as follows:
747: This is the general aircraft series.
-8: The 747-8 variant (in this case, a 747-...
- 54.3k
30
votes
Accepted
What is the reasoning behind using depleted uranium as counterweights in the 747?
Boeing
Boeing would have used DU because it had the right combination of physical characteristics and cost. Their tests showed that the radiation exposure for workers was low (2.6% of the statutory "...
- 26.3k
29
votes
Accepted
Is the entire length of a B747 or A380 wing used as a fuel tank?
Fuel tanks take most of the space in aircraft wings, but not all. There are other things on wings too. They are ailerons, flaps, slats, air brakes. On most airliners, the engines are attached to the ...
- 29.4k
28
votes
Are there any Boeing 747 still flying for commercial use?
There are many airlines still operating the 747 in passenger service. Lufthansa has bought the 747-8, the last delivery was in April 2015, so I'd expect that the 747 will be in passenger service for ...
- 82.8k
28
votes
Accepted
Are there any Boeing 747 still flying for commercial use?
There are still lots of 747's in scheduled passenger service and at least a few dozen of them will almost certainly remain so for the next 20+ years.
747-400
British Airways has 36 of them with ...
- 19.4k
28
votes
Accepted
What is this instrument for on the 747 flight engineer's panel?
It's for measuring the airplane's inclination on the ground for the longitudinal axis. There will be another one on a lateral bulkhead for measuring lateral inclination.
When doing fuel quantity ...
- 126k
26
votes
Would increasing the number of wheels of a Jumbo reduce the braking distance?
Typically, a little gain is obtained.
Larger airplanes use anti-skid technology. Anti-skid works by modulating brake pressure to ensure the tires never skid. It's important to understand the relation ...
- 768
26
votes
Accepted
Why do pilots cut the reverse thrust below 40 km/h?
The question speaks of a very old 747 landing tutorial. And as such I take that to mean it would be of a 747-100/200 aircraft, and that's the reference point I'm answering from.
First, concerning the ...
- 39.2k
25
votes
Accepted
Why are the largest civilian aircraft not adapted for military use?
There are several angles to this question, so I'll try to address what I think is important. My so-far short career has so far involved working almost exclusively with 747 derivatives, so I don't have ...
- 3,367
25
votes
Accepted
What are these silver stripes on Cosmic Girl for?
It's aluminum "speed tape" being used to run wires around the outside of the fuselage, possibly for load cells or some other kind of sensor related to whatever is being tested and that was impractical ...
- 126k
24
votes
Where does Air Force One refuel?
I can't confirm whether either VC-25 has refueled in flight while acting as AF1 but the aircraft is so equipped for the job.
I do know refueling on the ground depends on where the jet is and the ...
- 72.8k
23
votes
Accepted
What are these lines on the fuselage of a 747?
No, they are just the boundaries between skin panels. See below for a picture of the 747-8 fuselage during assembly.
[
Boeing 747-8 front from side (picture source)
And this is how the panels for ...
- 230k
22
votes
Does Nitrogen inside commercial airliner wheels prevent blowouts on touchdown?
Apart from the paragraph you quoted, here are a few more reasons.
Dry nitrogen is specified for aircraft use. I believe the rules say that any gas used cannot exceed 5% oxygen content. Because its ...
- 4,526
22
votes
Accepted
Why don't B747s start takeoffs with full throttle?
I can't give a 747 specific answer, but generally, on some engines it's desirable to let the engines stabilize at a moderate power setting, with the N1 equalized there, before advancing them to TOGA ...
- 126k
22
votes
Why does a Boeing 747-8 take more runway length to take off, compared to an Airbus A380?
This table compares some relevant numbers for the two aircraft:
Aircraft
Airbus A380
Boeing 747-8i
MTOW
575 000 kg
447 700 kg
Wing Area
845 m²
554 m²
Wing Loading
680 kg/m²
808 kg/m²
Thrust
4x ...
- 54.3k
21
votes
Can the A380 ferry an extra engine, like the 747?
The A380 does not appear to have the capability to transport an extra engine under the wing. Higher engine reliability combined with widespread availability of air cargo transport makes this option ...
- 100k
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