hydraulics and spoilers

[allflight57]

When I see aircraft in the maintainence hangar I see them with flaps down and spoilers extended most of the time, my question is how to the spoilers reamin up if the hydraulics aren't pressurized. Or is there a type of ground cart they use just to power them? thanks,

Tyer

[Clarence Oveur]

A lock is placed on the spoiler actuators when extended to mechanically hold them in the extended position.

[allflight57]

o ok thanks a lot, I appreciate it

Tyler

[allflight57]

sorry, but oone more question... how is it decided where to put the anti-collision lights on airliners? On the 757 the one on top is way up front and the bottom one is much farthur aft, but on the 737 they are very close to eachother, the top being only a couple feet in front of the bottom one. thanks again,

Tyler

[john_tullamarine]

The Design Standards (for example, FAR 25.1401 (http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=032357c11b8f01e6c63312d23a3d0a4a&rgn=div8&view=text&node=14:1.0.1.3.11.6.195.37&idno=14)) require a minimum volume coverage of the lights .. the OEM picks (generally at least two) spots which. in concert, achieve the design requirements.

At the end of the exercise you will have picked up a new word;

steradian - a solid angle at the center of a sphere subtending a section on the surface equal in area to the square of the radius of the sphere

isn't PPRuNe a wonderful sandpit of bits of information you really didn't set out to find ... ?

[Piper19]

allright... the spoilers that come up during maintenance are locked with retainers. On some aircraft the spoilers will remain up due to resistance in the actuator, even without hydr power. On the 757 they will remain up for a while; same with the elevator there that remains neutral after hydr shutdown, but goes down by time. A strong wind can blow them down, so it is still recomended to guard the spoilers if you work on them.

[Pontius's Copilot]

de Havilland, in their infinite wisdom, put only one red anti-collision beacon on the Q400: top of fuselage just forward of the wing 'hump' ... so it can only be seen from the forward quarter. It cannot be seen from vehicles waiting to pass behind on apron roadways or ramp vehicles/personnel unless in front of aircraft.

Airborne at night ... if you can see a red beacon, it's not a Q400; if it's got wingtip white strobes, it's not a Q400.