Airbrakes on Turboprops

[Airbanda]

A wee technical question.

Couple of hours ago twin turbo prop (Dash8/ATR?)passed over circa FL80- I am just west of Northampton so it was probably Brum inbound. Appeared to have petale type airbrake in tail like F28/146 deployed. Never noticed anything similar before. Which type has this and what are the speed/ altitude limitations on use?
TIA
Airbanda

[Jim lovell]

Dash 8's have no airbrakes

[Cardinal]

A Beech 1900 has large horizontal strakes on the aft section, these could be mistaken for the aforementioned petals.

[Nick Figaretto]

Never heard of a Turbo prop with an airbrake. The flight idle position is, for all practical purposes, an airbrake.

If an aircraft manufacturer thought it necessary to have increased "braking capacity" in the air, all they would have to do is to rate the flight idle lower. Alternatively, a way to pull the power levers a small notch behind "regular" flight idle.

Nick

[gaunty]

Nick
:eek:

[Nick Figaretto]

:D :D :D YES!!! I know what you are trying to say.

Pulling the PLs behind flight idle is not very smart... I know Fokker have made some computer analysis of "What will happen if I pulled the PLs into Ground Idle during flight?" The result was that IF the WOW-switch and the relees (?) in the pedestal fails, so that someone accidentally pulls the PLs to Ground Idle during flight, the airplane would lose some 20 000 ft in the recovery - IF the wings don't fall off. -Which they probably will.

What I am saying is, that I know that, for instance the Dash8 or a Beech King Air 200 has a larger drag (thus steeper descent profile) when the PLs are in flight idle than the Fokker 50. Similarly, a Cessna Caravan can keep almost Vmo till 5 miles final because of the extreme air-braking obtained when pulling the PLs to Flight Idle.

Thus - If the aircraft needed greater "air braking capability" it would be easier to make the aerodynamic drag from the propeller blades larger at Flight Idle, than making an extra, technically advanced and expensive air brake in the aircraft tail or on the wings.

To ensure that "speed brakes" is not used at normal descent, there could be 5 detent positions on the PLs: [list=1]
Max detent
Flight Idle
"Air brake"
Ground idle
Reverse[/list=a]

Just a suggestion to the aircraft engineers. :D

Any comments other than :eek: ?

We should have some of the engineers who are usually on "Tech log" to look at this. I will demand royalties :)!

Nick.

[Tinstaafl]

Nah, Nick, some smartarse would just come up with a differently named system...

-----------
Max detent

Flight Idle

Speed Reduction (tm)

Ground idle

Reverse
-----------------

NB All enquiries to 'Tinny's Amazing Devices, Inc'.

Quick (5 minutes) and convenient on-ramp/no downtime modifation kits to convert your turboprop from those other, unsatisfactory air braking methods to our unique speed reduction system. The supplied label maker is YOURS TO KEEP!

We firmly believe you get what you pay for. We charge extremely high premiums so you know it must be good!!

[Nick Figaretto]

Jeez, You stole my invention!!! ;D

Part from that - is my reasoning correct, then?

Nick.

[Hwel]

20,000 feet and the wings fall off, I dont think so.
Channex got an F27 into GFP not 6 months ago. The exact date escapes me its published on the AAIB website in the last 2 months. Ok so it went down like a brick, but it was eminently survivable. :cool: and indeed survive they did.

[PaperTiger]

Nick,

It's been tried at least once.
NTSB report (http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001213X30414&key=1) or another description (http://aviation-safety.net/database/1987/870304-0.htm)

[Tinstaafl]

Nick, it's obvious that my system is completely unrelated to yours, and is in fact a better system.

You can tell because it uses bigger words. :D

The premium version is now available, using recently developed 'Velocity Reduction' technology. This is available in a taxi in/taxi out bespoke services as well as the our well known field modification kits.

You sound like a forward thinking chap. Would you consider joining the research arm of 'Tinny's Technologies Ltd'** as a financial contributor & risk sharing partner. We're currently working on devices involving 'entropy'.


**'Tinny's Technologies Ltd' is a wholly owned research enterprise developing yet another fine product for 'Bastards Incorporated'

[Last Sector Power]

From what I believe the problem is if only prop goes into Beta / Flight Idle or if they both go in and only one comes out!!
Try hanging on to that One!! :eek: :(
It has happened in the past with deadly results.
Great fun in Cessna Caravan :D

[Nick Figaretto]

Paper Tiger & Whel: I read the articles. Jeez, even if they didn't lose 20 000 ft, it looks pretty scary anyway! That computer analysis that Fokker made may well have been a "worst case scenario," but I think the message comes trough: "Don't try to be a test pilot if you're not!"

Tinstaafl (what a weird name...): Wow, you've gor it all figured out, haven't you! 'Entropy' sounds pretty risky. I think I'd go for 'entalpy' instead :D.

Last Sector Power: You're probably right. I've also heard of incidents (or "near" incidents) where the A/C has experienced a sudden, strong yaw on final, because the flying pilot has tried to put the PLs just a "little bit" behind Flight Idle to make a shorter approach. :eek:

Nick

[Airbanda]

Thanks for all the replies, all that about the props and no need for airbrakes makes eminent sense. Looking in the spotters guides today,think cardinal probably has the answer.

[Pdub]

Weird name? just need to brush up on your anacronyms Nick. Tinstaafl, I'll have a ploughmans, and your buying ;)

[ 16 July 2001: Message edited by: Pdub ]

[ 16 July 2001: Message edited by: Pdub ]

[Tinstaafl]

No worries. You get the beer. Mine's a Guinness thanks. :D :D

[EX FTE]

You mistook a Cardinal for a DASH8/ATR???? As the former lead FTE on one of the DASH8 flight test aircraft I should take the hump at you misidentifying my pride & joy!

As for placarding on the quadrant, you will find that FAR/JAR Pt25 is fairly strict on what labels are used for each position on the condition levers.

As for going into the ground beta range while in flight. Yes it has been done before on the larger commuter aircraft and a few engines have been oversped as a result! The gate to go from flight range to grond range requires lifting "triggers" to allow the levers to move further aft. Therefore, pilot action is required to go behind the "gate" so you can surmise how these in flight occurrences occurred!!

It should be reassuring to know that the authroities are now pushing beta lock-outs that will prevent selecting levers behind the gate in flight.

As for airbrakes; all comments about the big egg beaters being good airbrakes are perfectly true!

If you want to be a really techno whizz, you dont actually need condition levers. Through the wonders of FADEC and PEC (propeller electronic control) the balde angle is automatically controlled by the PEC while the FADEC sorts out the torque.

Hope this answers the question.

[Bullit]

If you try to pull the trigger on a Dash 8 power lever you will hear an annoying sound. We call it the cockpit bird and use it to gain attention of the F/As` or to distrack them. A propaircraft with real airbrakes is the Transall used by the german army. Some of the Transallguys who joined my company told me they are really effective for so called Sarajevo approaches. On some regular approaches I think they`ve forgotten sitting on a Dash 8...check altitude...check pitch...check speed...check...aaaahhhh

Prost

[Airbanda]

Ex FTE- I was trying to say that somebody using the name Cardinal gave the most likely reply to my question. I might be a bit limited in middle age but I can still count engines!!