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jan_de_jong(at)casema.nl
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 Posted: Fri Jan 10, 2014 3:24 pm Post subject: How to Toggle Speed Brakes with Momentary On Switch? |
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jan_de_jong(at)casema.nl
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| Posted: Fri Jan 10, 2014 3:49 pm Post subject: How to Toggle Speed Brakes with Momentary On Switch? |
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(trying again - text in original was invisible)
Latching relays can be had with one of (at least) the following modes of
actuation:
- a set coil and a reset coil, possibly with the + terminals in common
- one coil with different polarity for set and reset
- one coil with the same polarity for set and reset (toggle action)
Jan de Jong
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racerjerry
Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY
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| Posted: Sat Jan 11, 2014 3:53 am Post subject: Re: How to Toggle Speed Brakes with Momentary On Switch? |
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Are you certain that momentary switch controlled speed brakes (latching up and down) are a good idea? I can see you getting in trouble during a go-around situation where you are busy applying power/setting flaps/killing carb heat/raising gear and losing track of speed brake position. During go-around, you are too darned close to the ground and eyes must be outside the airplane and control positioning must be achieved by ‘feel.’
I have no experience with speed brakes and I could be dead wrong, but I think this is at least worthy of consideration.
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Jerry King |
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kleh(at)dialupatcost.ca
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| Posted: Sun Jan 12, 2014 7:45 am Post subject: How to Toggle Speed Brakes with Momentary On Switch? |
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On 12/01/2014 10:14 AM, mmayfield wrote:
| Quote: |
nuckolls.bob(at)aeroelect wrote:
> Suggest you purge the term "speed brake" from your
> language used to talk about this system. It's
> a spoiler system that kills lift . . . designed to
> INCRASE rate of descent without materially
> increasing forward velocity. A speed brake puts
> out DRAG intended to slow the forward velocity.
>
> A pilot flying a Lanceair IVP with Precise Flgiht found
> himself on short final to the rocks out in California
> a few years ago. Check out the narrative paragraph
> 3 here http://tinyurl.com/m3zxgpw
>
> His deployment of "speed brakes" in fact increased
> his downward velocity. The Precise Flight system
> is not a speed brake.
>
Unfortunately I'm going to have to disagree with Bob here! I'd suggest the term "speed brake" is quite appropriate when looking at how the Precise Flight system is designed to work. so it's no surprise that the company have named them "speed brakes".
Spoilers are designed to reduce lift and moderately increase drag. They do so by creating a controlled stall over that section of the wing immediately behind them. Speedbrakes are primarily designed to increase drag with minimal effect on lift.
On the Boeings and Airbuses I've flown in my day job you'll see the lever which actuates the spoiler panels labelled "speed brake". On the ground, they function as lift dumpers. In the air they function as speed brakes. The function is defined by how many spoiler panels extend and to what degree. On fighter jets the "speed brake" is normally a pure speed brake - panels extending from the fuselage and having minimal to no effect on lift.
Going by the photos on their website, the Precise Flight system is narrow perforated flat plates extending perpendicularly from the wing. I'd suggest this is a classic speed brake design characteristic, not a spoiler design at all, even though it's on top of the wing.
The increased drag of speed brakes, or reduced lift/increased drag of spoilers, can both be used to either increase descent rate or reduce forward speed. The dominant effect on flight path depends entirely on what the pilot does with the pitch attitude of the aircraft. It does not necessarily define whether they're primarily "spoilers" or "speed brakes".
Food for thought. [Wink]
--------
Mike
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But large aircraft do use them differentially for roll control and they
ALL increase stall speeds and sink rates.
Sometime semantic connotations linger. Professional pilots have
inappropriately pulled the handle labeled "speed brakes" while
forgetting about the stall speed increase.
My caution here would be to make sure that the things automatically
retract if the throttle is firewalled regardless of what one calls them.
Ken
do not archive
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