Why?

[rickshaw]

Just a general thread to post general questions in.

Why are propeller blades black on post-WWI aircraft?

Ditto for Helicopter rotor blades?

Why do/did some air forces paint their aircraft in camouflage and then put high visibility panels with bright colours on them?

Why did the Avrocar fail?

[Thorvic]

I think the blades were painted black to show where they are when in proximity to the ground and ground crew.

The camo aircraft getting ID panels relates to the camo being too effective and ground force or even freindly air cover not being able to identify friend or foe and getting shot at or shot down

[McColm]

Ground crew have a habit of walking into parked aircraft. Even if you put a bright orange cover over a Warrior personnel carrier, some fool is bound to hit it!

[NARSES2]

Not all prop blades post war were black some metal ones were left that way and to be pedantic the Luftwaffe used very dark green - I'll get my coat 

Anyway I thought they were painted black to stop them reflecting sunlight into the pilots eyes, also to stop the same reflection being picked up by the enemy. The yellow/multi coloured tips were to stop the groundcrew walking into them, again the Luftwaffe were different and didn't use coloured tips.

The bright ID panels were as Geoff says an attempt to prevent friendly fire, especially from the ground, or when escorting bombers

[Mossie]

Ground crew have a habit of walking into parked aircraft. Even if you put a bright orange cover over a Warrior personnel carrier, some fool is bound to hit it!

I had to put red and white hi-viz tape on a stair case at work because several students banged their heads hard.  I argued that if they couldn't see a white landing that was at eye level they wouldn't see the tape, I was vetoed on that one!

The yellow/multi coloured tips were to stop the groundcrew walking into them, again the Luftwaffe were different and didn't use coloured tips.

My Grandad was groundcrew on Mossies, I remembering mentioning that the edict came in to paint the tips due a nasty incident.  It was heavy fog, a full crew had got disoriented and walked into the blades.  I think he mentioned it was USAAF.  The memory (both his and mine!) might be slightly fuddeled but that's how I remember it.

[Dizzyfugu]

Colorful markings on top of cammoed aircraft is in most cases for quick ID purposes, be it for ground forces (esp. AA guns) or air combat. Some aircraft also have very similar shapes or are even used by both sides, e .g. the Mirage III in the clashes between Isreal and Egypt, or the Super Mystere which was at casual glance very similar to the Su-7 on Egyptian side. Hence, Israel introduced the huge orange/black triangles.
Additionally, a quick ID in air combat can be vital - more than the camouflage effect which is to hide the thing.

Concerning prop blades in black: I think the reflection effect and block of vision for the pilot is the most important issue on normal aircraft. A light color reflects more light, and the blurring effect can be ver distracting. I know that in WWII Japan experimented with six-bladed propellers, and they were rejected on single-engined puller fighters because the blurring was inacceptable!
BTW: even blank metal props (e .g. pre WWII USN) had black rear sides.

On helicopters I can imagine that the cammo effect is more important. A rotating rotor is a big area, and with a light color it is very well visible from above. I'd guess that it is a Vietnam era thing/learning. More modern helis have lighter blades, though, might be the result of different materials and their resilience to environmental effects, so that a paint protection is not necessary anymore (but could be quickly applied)?

[The Rat]

Why did the Avrocar fail?

Because they didn't realise that they had actually invented the hovercraft. If they had the things might have turned out differently.

[NARSES2]

I know that in WWII Japan experimented with six-bladed propellers, and they were rejected on single-engined puller fighters because the blurring was inacceptable!

Now that's interesting. I've got a kit of a Japanese experimental/prototype fighter with a 6 bladed prop option. Didn't realise it was a no-go, would look good though 

[McColm]

The North American RA-5C wore camouflage during Vietnam on a few aircraft, the F-4 pilots had problems identifying them. Hence the bright coloured tail fins.
As to the Avrocar stability was the main problem, research shows that although the Avrocar could travel fast in forward mode, VTOL handling was a nightmare.

[The Big Gimper]

The North American RA-5C wore camouflage during Vietnam on a few aircraft, the F-4 pilots had problems identifying them. Hence the bright coloured tail fins.
As to the Avrocar stability was the main problem, research shows that although the Avrocar could travel fast in forward mode, VTOL handling was a nightmare.

Besides the RA-5C which looks cools in camo BTW, the A-4, F-4 and R/KA-3B were trialed. Although I can't recall the source, the dark colours were a big issue with visibility at night when working on a crowded aircraft carrier deck.

Wolfpack decals did a few in 1/72:

A-4E
F-4G
KA-3B
RA-3B

[Hobbes]

Concerning prop blades in black: I think the reflection effect and block of vision for the pilot is the most important issue on normal aircraft. A light color reflects more light, and the blurring effect can be ver distracting. I know that in WWII Japan experimented with six-bladed propellers, and they were rejected on single-engined puller fighters because the blurring was inacceptable!

Interesting, given e.g. the Spitfires and Wyverns with contraprops with 6 or more blades...

[RotorheadTX]

The Swedes tried camouflaging the blades on their splinter-schemed HKP-4's (CH-46/KV-107/Sea Knight) - on the ground it was wonderful, in flight they found it made the appearance of concentric coloured circles - NOT a great idea after all. They went back to black blades like everyone else.

http://i191.photobucket.com/albums/z311/fredtulloch/PC100427.jpg

[GeorgeC]

Ground crew have a habit of walking into parked aircraft. Even if you put a bright orange cover over a Warrior personnel carrier, some fool is bound to hit it!

Not necessarliy.  They may have the presence of mind to get into an airfield vehicle first to ensure maximum damage to the aircraft and an unserviceable vehicle...

[Geoff]

My Grandad was groundcrew on Mossies, I remembering mentioning that the edict came in to paint the tips due a nasty incident.  It was heavy fog, a full crew had got disoriented and walked into the blades.  I think he mentioned it was USAAF.  The memory (both his and mine!) might be slightly fuddeled but that's how I remember it.

My dad told me a similar story - He was on Beaufighter nightfighters and one of the groundcrew ran into a turning prop with predictable results.

[wikxie]

I heard one story of a ground crew member that walked through the arc of a turning propeller and survived, but when he realised what he'd just done he quickly stepped back... he wasn't lucky twice.