A

Andrew Griffin

Member
I recently had the opportunity to fly a Columbia 350 which has the Precise Flight SpeedBrakes installed.

http://www.preciseflight.com/viewpage.php?pID=8

I really enjoyed the flexabilty that the speed brakes added to the aircraft.

I was wondering if anyone has (or has considered) installing these on an RV? And whether people think they would be as affective as they are on something like the Columbia or other aircraft like mooney's and cessna's that I saw fitted with them at OSH.

I emailed the company with this query and have to date recieved no response.

What are peoples opinions of speed brakes on RV's? I know that RV's aren't normally considered high performance enough to need speed brakes, however the Columbia I flew only did 180 knots and some of the aircraft that I have seen with them fly at speeds a lot lower than a RV.

On top of all of this I just think they look really good... Which is of course a reason in itself!!
 
Costs

You know that the costs of these suckers are about 3.5K! Plus then utilize a pretty large controller and you'd have to make room for that. I'm building a Legacy, that even has the box all ready built in the wing for them and I"m not going to install them. If you are a highperformance aircraft, then maybe, but when I say hi-performance, I'm talking 200+kts and flight level altitudes. *and* need the ability to "rapidly" change altitudes.

Oh, they'd work on an RV, but it begs the quesiton..... "Why?".... Yes, I know... "cuz you can"...
 
I suppose the question really is "what would I like on my aeroplane and do I have a use for it?" Those speedbrakes certainly look good, would provide a new aspect to its performance envelope and would be good fun to operate so GO FOR IT!

Regards.
 
No..........

Why??

More weight, more cost, more complexity............kinda like having a ballistic recovery parachute on a Skyhawk.........RVs are not THAT fast,
Regards,
 
Speedbrakes

Why not? The issue of cost is irrelevant considering any amount of money can be expended on flight instruments, navigation equipment, paintschemes, interior fit (to name a few) not to mention the weight penalty that those items incur.

Does anyone have any technical data on speedbrakes that they would care to contribute? Links to websites containing such information would be greatly appreciated. It would be very interesting to hear from anyone with hard facts borne from personal experience concerning the fitment of speedbrakes to their own aeroplanes; handling advantages or otherwise, difficulty of fitment, ease of operaton, type of stick grip used, weight penalty, cost, tricks and traps for young players etc.

It is very hard to argue with science; last time I checked the world was still round.

Thanks in advance.
 
Belly Version?

Not that I would do it, but I recall someone putting a speed brake on a Moni Motorglider which deployed from the belly. It would not be a spoiler, but it would have lots of drag. He used a plate with lightening holes and a simple cable actuator. FYIO.
 
CS PROP

I gave them alot of consideration. One unit under the fuselage, seemed the best choice on the -8. But, Alan is right, they are very very expensive. I called the company a few years back and they were not interested in selling any one at a time. They only wanted to support their 2 units kits.

Also, remembered that I will have a pretty good speed brake up front, CS prop, especially with the 3 blades.
 
It's been done....

hevansrv7a said:
Not that I would do it, but I recall someone putting a speed brake on a Moni Motorglider which deployed from the belly. It would not be a spoiler, but it would have lots of drag. He used a plate with lightening holes and a simple cable actuator. FYIO.
Click to expand...

This was also a part of the design of the Smyth Sidewinder, an old home built - EAA Best Design in 1969 - which along with the T-18, might be considered a "precursor" to the RV-6A and later RVs...

sidewinder101.gif


gil in Tucson... remembering being impressed with T-18s in 1973...
 
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DIY. Thats the best shot if you want some. The kit just isn't worth the money (the shop I work at installed one on a 210 recently), to complex and pretty much annoying to install. I like the belly idea the best, the one upside of the precise flight ones is that they, when installed correctly, don't affect the airflow in a climb, just in a decent.
 
I don't know all the facts, but there are actually 2 companies that make speed brakes... They are also somehow related as they have sued one another before over design right, etc.

Here's the other one.... Oh, and they aren't any cheaper here vs Precise Flights version..

http://www.speedbrakes.com/
 
Alan, I see those... interesting. Anyway, I think speedbrakes are pretty much a waste on RV's, although if I was building a Legacy, espcially a FG Legacy, I would seriously consider them. They take a bit to slow down, and being that they aren't rated Aerobatic (only Utility) I don't know that I'd want to load it up in the overhead as much as I have the few 360's and Glasairs i've flown... I suppose you can always slow it down before the decent, but that cuts a bit of the Lancairs speed advantage down. Anyway... i'm sure you've already considered all that.
 
osxuser said:
Alan, I see those... interesting. Anyway, I think speedbrakes are pretty much a waste on RV's, although if I was building a Legacy, espcially a FG Legacy, I would seriously consider them. They take a bit to slow down, and being that they aren't rated Aerobatic (only Utility) I don't know that I'd want to load it up in the overhead as much as I have the few 360's and Glasairs i've flown... I suppose you can always slow it down before the decent, but that cuts a bit of the Lancairs speed advantage down. Anyway... i'm sure you've already considered all that.
Click to expand...

Maybe if I were building an RG, i'd go with them, but an FG, nope, don't need them. They slow down nicely expecially with a CS prop and the gear down and welded :)...
 
I always figured the FG would be harder to slow down since you can't toss that high drag gear out there, and the Fixed legs are faired much better, therefore much lower drag. But the nice 3-blade CS prop will help...
 
pierre smith said:
Why??
Click to expand...
Because you can, and it would make for larger flight envelope. Have had speed brakes in the back of my mind for the last 6-8 years, but just never acted on the idea.

I make a lot of overhead approaches. Being able to pop speed brakes out and drop at a decent airspeed appeals to me. Not sure I'd go with the wing-mounted type though. Interesting.

I've got a cs prop, but just not terrible comfortable with reverse loading the engine. I do it when necessary, just not wild about doing it regularly as a normal course of action.
 
Design?

Bryan,
You have a valid point about reverse-loading the crankshaft but I believe that I read somewhere that on the C/S engines, they are equipped with thrust bearings to accomodate pressure in either direction continually.

As an aside, I flew a friend's RV8 yesterday, equipped with a three-bladed composite C/S prop and I was absolutely amazed at the rapid deceleration as the blades went flatter on throttle reduction. A tremendous amount of braking and so much easier to slow down than my fixed pitch 6A.
Regards,
 
Burt Rutan designed a speed brake in many of his airplanes.

The LEZ and Cozy MKIV have a belly board and it is used on most every landing, but it has a structural speed limit of 90 knots, so it is not much good for a high altitude, high rate of descent. It also would cause an engine to overheat if the electric version did not retract. The primary purpose of the device is to provide for a normal glide (2-3 degrees) on final. Without the board, the approach was very flat or airspeed would build up when it should be constant. The aircraft have no flaps.

Does the RV not a speed brake? I think not, except as someone mentioned, it may have cosmetic appeal.

Commecial jets all have speed brakes, but they are almost never used. If there is a need, it usually means the pilot did not get the power off in a timely manner because he wasn't thinking much in front of the airplane. If speed brakes are used for whatever reason, fuel was wasted going too fast, too long. Commercial operators frown on wasting fuel. There is, however, a common emergency procedure with high altutude pressurized airplanes that requires speed brakes - sudden loss of cabin pressure and the need to descend quickly before everyone feezes to death or expires for lack of oxygen - usefull consciousness at 39000 without O2 is less than a minute, the OAT is colder than cold, like -40C - hopefully the crew will get a mask on quick and find a more friendly environment.

That's my one page disertation on speed brakes.

Save your money. Or spend it on a good auto pilot coupled to a GPS which will compute your descent and tell the AP when to start down if you don't feel like computing it in your head and flying the airplane. There's much magic in those black boxes and you'll never need those expensive boards, especially in an RV, which has a tendency to come down quick anyhow. :)

dd
RV-7A
N707DD
 
An exception....

David-aviator said:

Commecial jets all have speed brakes, but they are almost never used.

That's my one page disertation on speed brakes.
dd
RV-7A
N707DD
Click to expand...

Of course, there's always an exception.... :)
The BAe 146's I watched on approach to LAX when I drove by every day seemed to use their speed brakes every time....

http://www.airliners.net/open.file/1099075/M/

I particularly noticed this, since they seemed to have stolen the design from a carrier fighter from by youthful plane spotting days... :)

http://www.airliners.net/open.file/0351406/M/

Any US folks know what the plane is??
Copyright says I have to link only...

Back to RVs... a CS prop upgrade would be easier and not too expensive instead of a new design, and unknown aerodynamic issues, of a speed brake....

gil in Tucson
 
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What plane?

Re. the "what plane is it" above, it's a Royal Navy Buccaneer, the RN's equivalent of my old plane the A-6 Intruder; both carrier based, low level, all weather, attack (bomb dropping) aircraft. The communities were so close that the A-6 training squadron had an exchange Brit on staff. A-6s went away in '97, Buccaneers in the early 90s, I believe.

Doug Seward
Seattle area
-4, wings
 
Speedbrakes on any aeroplane expand its operating envelope. Their uses include but are not limited to:-
1. increasing rates of descent,
2. slowing down for any number of reasons,
3. protecting normally aspirated engines from thermal shock,
4. transfering the weight of the aeroplane from the wings to the wheels and therefore the brakes to ensure braking efficiency during the landing roll, to name a few.

They are standard fit to many aeroplanes and certainly most airliners. They are standard equipment to be used as per the manufacturers instructions.

They are not installed to correct pilot "error" due to his allegedly slow thought processes.

I guess what it boils down to is whether one has a use for the speedbrakes on one's aeroplane and whether one can justify the cost.

Thankyou to those who have provided technical information and website references in response to my enquiry.

Regards,
 
Thanks to everyone who has provided definitive technical data concerning speedbrakes.

One thing I haven't been able to find out about is whether installing speedbrakes on an RV8 interferes with the placement of the standard or "extra range"fuel tanks?

If anyone has personal experience of this or is able to direct me to a technical reference that information would be greatly appreciated.

Thanks in advance,
 
David-aviator said:
Commercial jets all have speed brakes, but they are almost never used. If there is a need, it usually means the pilot did not get the power off in a timely manner because he wasn't thinking much in front of the airplane. If speed brakes are used for whatever reason, fuel was wasted going too fast, too long.
Click to expand...

Not necessarily... yes, speedbrakes can be used to correct a pilot's mistakes, but there are other instances that require their use. How about when a controller keeps you high and fast on an arrival and you need them to make a crossing restriction? How about when you're following the FMC VNAV path but an increasing tailwind on descent bumps up the GS and the IAS follows? Or when you're all set up for an arrival to one particular runway, but ATC changes you on short notice to a closer runway? Yep, all of a sudden you're high and fast, gotta use the brakes.

As an airline puke, I try not to use 'em... they're not efficient, they're noisy and cause quite a bit of uncomfortable vibration. But having said that, they are installed and sometimes we gotta use them, and it ain't always to correct our mistakes.

John
 
Wouldn't spoilers be a better option?

From the AeroOptions,Inc. FAQ:
(My emphasis added)

Question :What is the difference between SpeedBrakes and spoilers?

Answer :A spoiler's primary purpose is to "spoil" the lift created by the wing. As such they are typically mounted near the MAC (Mean Aerodynamic Chord) or slightly forward, and when they're extended they do their job admirably, although they create only a modest amount of drag in the process because of their [low profile] shape and location. SpeedBrakes, on the other hand, are mounted aft of the MAC and are shaped in such a way to create more drag than lift reduction. This is why when the SpeedBrakes are deployed the nose of the aircraft needs to be lowered slightly to maintain airspeed while the power setting remains the same.

I've been thinking (others too, but especially) fixed pitch RV-9's would be a perfect candidate for spoilers - alledgedly "harder" to land because they have so much lift and want to keep on flying! In gliders, spoilers give precise glideslope control with no change in speed or attitude, then full open to keep it on the ground... sounds perfect!
I hear about speed brakes, but are there any spoiler packages out there that anyone has any experience with?
 
Very neat Pic of an EZ, Cal. Thanks. Brings back lots of good memories :)

Bill DC9 driver, you're right, sometimes boards are necessary. That's why they are installed. On the 9, slats were much more civilized, they didn't shake as much.

But I am not changed of mind on the RV, speed brakes are a waste of $$, at least a waste of my money.

dd
 
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