NTSB Safety Alert CH 601

Brian Whatcott wrote:
Here's a model report on treating home-builders like grownups.
Highlights:
Mass balancing controls - tight control wires not enough

Reduced stick force per G at higher G made worse by aft CofG

Don't push the stick hard by mistake - it may be your last.

http://www.ntsb.gov/recs/letters/2009/A09_30_37.pdf

Brian W


I forgot to mention a tactic used for improving pitch stick force per G.
Where an elevator rod or wire is connected by a pulley wheel or lever
- a mass on a fore and aft lever arm from the pivot provides a turning
moment which increases with increasing g, so as to increase the reaction
to elevator control force with g. This was the tactic used on the
Spitfire, if I remember....
There's another mass that is not structural like surface balances.

Brian W

On Apr 19, 6:39 pm, Brian Whatcott wrote:

I forgot to mention a tactic used for improving pitch stick force per G.
Where an elevator rod or wire is connected by a pulley wheel or lever
- a mass on a fore and aft lever arm from the pivot provides a turning
moment which increases with increasing g, so as to increase the reaction
to elevator control force with g. This was the tactic used on the
Spitfire, if I remember....
There's another mass that is not structural like surface balances.

That's called a bobweight, and it's to give the pilot some sense of
the stress he's putting on the airframe. Many current aircraft use it.
Even the Cessna 185, IIRC, has it. See a service bulletin regarding
the bobweight on the Citation:
http://www.tc.gc.ca/CIVILaviation/ce...rt/1999-05.htm

Dan

On Apr 19, 7:55*pm, wrote:
See a service bulletin regarding
the bobweight on the Citation:
-------------------------------------------------------------------

Dear Dan,

On the Citation I believe you will find it is called the 'Robert
Mass'.

:-)

Wanna see an airplane break up from flutter?

Watch the movie clip:

http://www.velozia.com/?p=1387

BTW, the Auguste Raspet Memorial Department of Aeronautical
Engineering at Mississippi State University does flutter testing on
airplanes, including experimentals. Bring your checkbook.

White Lightning designer and Citadel-educated engineer Nick Jones had
the White Lightning successfully tested there.

I have balanced a set of flight controls with lead embedded in the
leading edges--- rudder, elevator, ailerons --- for the White
Lightning; and no, they are not completely balanced, just enough to
avoid flutter up to about 350 kts. This is a 220 kt. cruise aircraft.

jl wrote:
Wanna see an airplane break up from flutter?

Watch the movie clip:

http://www.velozia.com/?p=1387

BTW, the Auguste Raspet Memorial Department of Aeronautical
Engineering at Mississippi State University does flutter testing on
airplanes, including experimentals. Bring your checkbook.

White Lightning designer and Citadel-educated engineer Nick Jones had
the White Lightning successfully tested there.

I have balanced a set of flight controls with lead embedded in the
leading edges--- rudder, elevator, ailerons --- for the White
Lightning; and no, they are not completely balanced, just enough to
avoid flutter up to about 350 kts. This is a 220 kt. cruise aircraft.


Great post! That flying wing breakup looked kinda like a divergent
pitch oscillation to me. There is nothing like a first hand account
of a surface balancing - any idea what proportion of the control
surface weight was balanced? That would be an interesting value!

Regards

Brian W

jl wrote:
Wanna see an airplane break up from flutter?

Watch the movie clip:

http://www.velozia.com/?p=1387

Here's the proper way to handle flutter:

http://www.youtube.com/watch?v=a-qS7oN-3tA

Sorry - it's an experimental aircraft in the traditional sense, so probably
not topical for a "homebuilt" group. ;-)