Aviation trivia quiz.

a reply to: Imagewerx

I thought it was due to the higher than standard internal cabin air pressure that the Comets were using. That was causing stress fractures around sharp corners of the windows and was causing failures at altitude. IIRC they fixed that issue on later models that had more rounded windows. That is the reason why most all airliners to this day have rounded windows.

a reply to: Sammamishman

With square cuts like that even normal pressure is going to cause a failure much faster.

a reply to: Sammamishman

I was sort of right about the rivets being a contributing factor in this......

The RAE also reconstructed about two-thirds of G-ALYP at Farnborough and found fatigue crack growth from a rivet hole at the low-drag fibreglass forward aperture around the Automatic Direction Finder, which had caused a catastrophic break-up of the aircraft in high altitude flight.[115] The punch rivet construction technique employed in the Comet's design had exacerbated its structural fatigue problems;[97] the aircraft's windows had been engineered to be glued and riveted, but had been punch riveted only. Unlike drill riveting, the imperfect nature of the hole created by punch riveting could cause fatigue cracks to start developing around the rivet. Principal investigator Hall accepted the RAE's conclusion of design and construction flaws as the likely explanation for G-ALYU's structural failure after 3,060 pressurisation cycles.[N 21] The Cohen inquiry closed on 24 November 1954, and although the inquiry had "found that the basic design of the Comet was sound",[110] de Havilland nonetheless began a refit programme to strengthen the fuselage and wing structure, employing thicker gauge skin and replacing all square windows and panels with rounded versions.[109]

a reply to: JIMC5499

Guess it does look like a 'Bristol' but it's an Australian made 'Woomera' for WW2.

a reply to: Imagewerx

I was taught in school that stress at the end of a crack is infinite. This is why you stop drill a crack before putting a strap on it. It is also why you always put a radius on an inside corner of a laser cut part. That's how a Junior Engineer created $60,000 worth of scrap when he didn't listen to a Mechanical Designer with 15 years of sheet metal experience. That's what made this Mechanical Designer, get his engineering degree.

originally posted by: Barnalby
a reply to: Sammamishman

Aka even more (finicky, 1950's) throttle points to control separately in an attempt to keep the damned thing airborne.

There's a reason why my example, and it's legendary predecessor, used only one engine, with bleed valves for fine control...

The Harrier was the successor to the P1154, not its predecessor. It was developed to salvage something useful from the cancellation.

Also, PCB was giving Rolls Royce serious headaches well into the 1980's (P1214) so we cannot realistically expect the P1154 to have performed as expected.

originally posted by: Zaphod58
a reply to: Sammamishman

With square cuts like that even normal pressure is going to cause a failure much faster.

The steel used for the fuselage skin was also of too thin a gauge so it cracked easily. Comet 4 (and everything else) had a thicker skin.

What achievement do the Vickers Viking, Fairchild C-123 and SNCASO SO30 all have in common with each other?

a reply to: waynos

They have both reciprocating and jet engines on them.

The VHF civil aircraft comms band (108-136 MHz) and UHF military comms band (225-400 Mhz) both use the older standard AM (Amplitude Modulation) method of sending the signal against the newer and considered to be better FM (Frequency Modulation).

Why do they use AM instead of FM?

a reply to: JIMC5499

That's true, but it's not an achievement. (One more step)

Come on guys,someone must know why AM and not FM?

a reply to: Imagewerx

Just a guess, but is it because AM has longer range and can have more channels per bandwidth than FM? Oh, and it can reach around obstructions like mountains and such?

a reply to: waynos

They all have a connection to Rolls-Royce? The Vickers and the Sub Quest used Rolls turbojets, the C-123 used a Allison turbo prop that is now being produced by Rolls.

originally posted by: Sammamishman
a reply to: Imagewerx

Just a guess, but is it because AM has longer range and can have more channels per bandwidth than FM? Oh, and it can reach around obstructions like mountains and such?

FM has marginally better range and is more efficient with regards to transmitter power,and AM with it's sidebands takes up more bandwidth than FM does.VHF and upwards is line of sight regardless of how the signal is encoded to the carrier wave,neither will go though solid objects such as mountains or similar.

This is more to do with 121.5Mhz,but applies equally to all other frequencies.

121.5 is Guard frequency. I'm going to hazard a guess and say that it is easier for locating the source of a signal with AM than FM. I remember our radio compasses being AM and being able to determine a rough position by plotting the reciprocal bearings of radio stations.

originally posted by: Imagewerx

FM has marginally better range and is more efficient with regards to transmitter power,and AM with it's sidebands takes up more bandwidth than FM does.

Try again...

originally posted by: JIMC5499
121.5 is Guard frequency. I'm going to hazard a guess and say that it is easier for locating the source of a signal with AM than FM. I remember our radio compasses being AM and being able to determine a rough position by plotting the reciprocal bearings of radio stations.

NDBs and similar are AM for the same reason as the comms channels are at a guess.FM has much better noise rejection than AM does,but this isn't what I'm after here.

What happens on AM when two different radio operators transmit at the same time,and what happens on FM?

originally posted by: RadioRobert

originally posted by: Imagewerx

FM has marginally better range and is more efficient with regards to transmitter power,and AM with it's sidebands takes up more bandwidth than FM does.

Try again...

FM broadcast takes up a lot more I know,but we're talking about a much narrower bandwidth comms band here?

originally posted by: Sammamishman
a reply to: waynos

They all have a connection to Rolls-Royce? The Vickers and the Sub Quest used Rolls turbojets, the C-123 used a Allison turbo prop that is now being produced by Rolls.

No it's not that.

Conversions of each type were the very first pure jet powered transport aircraft to fly in their respective countries, UK, USA and France