Rear view mirrors on planes

[Captain]

To see the exhaust flame for setting the mixture?

Dan

oooh, there's a good guess.

If that's not it does it have anything to do with the three foot'ish long tubes mounted on the bottom aft of each engine?

 

[Pilawt]

The mirrors on the Ju.52 were the prop synchronization system.

When the pilot looks at the mirror on the #1 nacelle he sees the reflection of the #2 (center) prop -- through the arc of the #1 prop. Stroboscopic effect lets him precisely synchronize the two. The co-pilot repeats the process on the right, and voilá -- er, Und sieh da! -- all three are synchronized!

 

[Captain]

Interesting. Don't think I ever would have guess that.

Do you know what the cluster of white tubes are?

 

[MultiMediaWill]

The mirrors on the Ju.52 were the prop synchronization system.

When the pilot looks at the mirror on the #1 nacelle he sees the reflection of the #2 (center) prop -- through the arc of the #1 prop. Stroboscopic effect lets him precisely synchronize the two. The co-pilot repeats the process on the right, and voilá -- er, Und sieh da! -- all three are synchronized!

How do we know anything you just said is true? It doesn't make any sense seeing as engine startup times vary and therefore nearly impossible for humans to manually synchronize propellers.

 

[Captain]

How do we know anything you just said is true? It doesn't make any sense seeing as engine startup times vary and therefore nearly impossible for humans to manually synchronize propellers.

Synchronizing the propellers has nothing to do with starting the engines. It's something done inflight. Humans do it all the time.

 

[EdFred]

How do we know anything you just said is true? It doesn't make any sense seeing as engine startup times vary and therefore nearly impossible for humans to manually synchronize propellers.

It's not to synchronize engine times. When you have multiple props spinning at different speeds you get a "whoom whoom whoom" sound that can get quite annoying as the sound waves spike and cancel each other out at certain harmonics. When you get all the props turning at the exact (or almost exact) RPM, the sound goes away. That's what prop synching is.

 

[JOhnH]

What about a horn, that would seem more useful...

I would have LOVED to have had a real loud horn a few years ago. Our engine had a catastrophic failure and we had to put down on a divided highway during rush hour. Just as we were about to settle on the highway, a little red pickup truck came up underneath us from behind. He had to see us and without power, we couldn't do much but pull up which caused us to stall and slam the ground and bounce. With the high tension power lines on the right, we pushed it to the left across the grassy median and up onto the other side, into oncoming traffic. But at least they all saw us and pulled off to the side. It reminded me of Moses parting the seas the way we taxied down the center line and everyone pulled out of our way. Except for that damn road sign that tried to argue with our wing. (The wing won, but it was still cheaper to replace the sign that repair the leading edge).

But I would have LOVED a real loud air horn to blast that crap out of that pickup driver.

 

[Pilawt]

Do you know what the cluster of white tubes are?

No, I don't. There's a set under each engine, in the prop blast. Venturis? Some kind of wind-driven generators?

[Edit] I found a Ju.52 manual online. Those are Schmierstoffkühleren -- oil coolers!

 

[weilke]

You can see quite a few tip-tank-equipped airplanes (e.g. Bonanzas, Comanches) with mirrors on the inboard side of the tanks, just for that purpose. Also, some Cessna Centurions have mirrors hanging down from the underside of the wing.

'Three green, two in the mirror'

Even comanches without tips often have those mirrors.