Happy-flier
Topic Author
Posts: 286
Joined: Sat Dec 25, 1999 4:41 pm

Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Thu Aug 26, 2004 8:24 am

I have wondered for a while whether pilots use both engine reverse and spoilers when landing Dash 7s (depends on conditions, I guess), or usually one or the other. The reason I ask is that with four engines even in reverse idle, wouldn't the spoilers be rendered completely ineffective due to the disruption of airflow over the wings? I'm picturing the scenario and it has me curious.

OR ... do Dash 7s typically land at such slow speeds anyway, that deployment of all possible air-brake devices is rarely necessary?

I'd appreciate any insight. Thanks.
May the wind be always at your back . . . except during takeoff & landing.
 
320tech
Posts: 489
Joined: Mon May 17, 2004 11:38 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Thu Aug 26, 2004 9:07 am

I haven't worked on the Dash-7, but the Dash-8 automatically deploys flight spoilers (and ground spoilers, before they were de-activated) upon touchdown. I suspect pretty strongly the -7 is the same. Reverse thrust is selected by the pilot to suit the situation, so it's entirely possible that both spoilers and T/R would be used.

The flight spoilers are located just inboard of the ailerons, and so wouldn't be affected by airflow from the engines.
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
 
WrenchBender
Posts: 1662
Joined: Wed Feb 04, 2004 5:59 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Thu Aug 26, 2004 10:12 am

If you look at the development of the DeHavilland Canada line
-2 Beaver,
-3 Otter,
-4 Caribou, no spoilers
-5 Buffalo, Spoilers for short field work
-6 Twin Otter, Spoilers on the 300S STOL Commuter
-7 Spoilers (DHC still thinking Short/STOL Ops)
-8 Spoilers again carryover from the STOL heritage.

For some reason the DHC design group was still thinking in terms of STOL performance and rough field capability during development of the Dash 7. Much like the 300S Twin Otters which didn't really need spoilers but they were designed and installed in anyway, it's just the way DHC did things. Too bad there isn't a design team out there to propose some capable new concepts for these so called Bush Planes (-2 thru -6).

WrenchBender
Silly Pilot, Tricks are for kids.......
 
320tech
Posts: 489
Joined: Mon May 17, 2004 11:38 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Fri Aug 27, 2004 2:09 pm

Yeah, I always thought that de Havilland missed the boat when they didn't design a Beaver / Otter replacement in the early nineties. Of course, they may have had other things to think about (strikes, bankruptcy, buy-outs, etc).
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
 
beowulf
Posts: 743
Joined: Wed Jul 30, 2003 3:22 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Fri Aug 27, 2004 4:14 pm

Hi,

An interesting issue Wrenchbender brought up here. Is another manufacturer picking up from DeHavilland? Sooner or later these bushplanes need to be replaced? Are there other replacements out there? Moreover, the question is, is there a market for this bush planes?

Nick
 
Yikes!
Posts: 284
Joined: Sat Oct 13, 2001 4:51 pm

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Sat Aug 28, 2004 8:47 am

There have been only 124 Dash 7's built. One of which was a high-gross-weight version DH7-150-Ice Reconaissance model which was certified to a 47,000 lb GTOW (approximately).

One of the biggest drawbacks to the DH7's acceptance into the commercial market was its speed. At 220 KTAS it was slow. Very, very slow. In the meantime the DH8 and its PW100 engine was in the fast-track development stages. A lot of prospective buyers told DHC that if it could produce the DH7 airplane with the equivalent of a -65 engine (~1300 shp) they would consider its purchase. Enough hesitation existed to halt the DH7's production as PWC would not do the R&D necessary without sufficient up-front orders for its engines. A few years later, Shorts Brothers was able to make the necessary guarantees with the S-360 version. And so the engine was finally developed that would have made (or Could have made) the DH7 a commercial success.

I was lucky enough to have flown the type as well as the -150 IR. The short field capabilities of the type just aren't required anymore. At least on a regular basis.

The frontiers of aviation continue to fade into the past....

 
ScooterTrash
Posts: 553
Joined: Thu Aug 02, 2001 10:39 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Sat Aug 28, 2004 9:00 am

You are right about the STOL performance not being required anymore... Or is it? Imagine the capacity improvements at large airports if STOL capable aircraft could use shorter runways.

Personally, I think these RJ's with jet-like runway requirements are the worst thing to happen to airports since the TSA (sorry- had to get a dig in there).

Scooter
 
320tech
Posts: 489
Joined: Mon May 17, 2004 11:38 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Sat Aug 28, 2004 9:13 am

As far as replacing the old Beavers and Otters goes, think Cessna Caravan and Grand Caravan. The only reason they haven't taken over entirely is the huge price tag. It's still much cheaper to rebuild a Beaver / Otter than to buy a Caravan.
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
 
Yikes!
Posts: 284
Joined: Sat Oct 13, 2001 4:51 pm

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Sat Aug 28, 2004 9:42 am

No argument here with regards that prehistoric rendition called the TSA.

"They" just don't get it. And never (from my perspective) will.

STOL requirements are now few and far between. For those that do require it though, there are sufficient numbers of DH7's available. Unfortunately the -65 retrofit is not available.

 
Slcpilot
Posts: 562
Joined: Thu Aug 07, 2003 3:32 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Wed Sep 01, 2004 7:07 am

-2 Beaver,
-3 Otter,
-4 Caribou, no spoilers
-5 Buffalo, Spoilers for short field work
-6 Twin Otter, Spoilers on the 300S STOL Commuter
-7 Spoilers (DHC still thinking Short/STOL Ops)
-8 Spoilers again carryover from the STOL heritage.


Are there any plans for a -9? And no list is complete without my favorite DHC....

-1 Chipmunk !


SLCPilot

Who, incidently, has never flown/been a pax on any DHC product...
I don't like to be fueled by anger, I don't like to be fooled by lust...
 
User avatar
Starlionblue
Posts: 17053
Joined: Fri Feb 27, 2004 9:54 pm

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Wed Sep 01, 2004 7:23 am

There are probably plans for a 9, but since the -8 is selling rather nicely...


Starlionblue, who has flown the Twin Otter and the DHC-8-Q400.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
atct
Posts: 2472
Joined: Fri Mar 16, 2001 6:42 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Wed Sep 01, 2004 9:20 am

Yea the Caravan is sorta an Otter replacement. But what mechanic can just sit down in the woods and fix up a 208 with a light misty alaskan rain and mud beneath him. That picture just doesnt come to mind, now a veteran Otter/Beaver, just seems to suit the theme better. Also the performance of the DHC's vs. teh Caravan still leaves something to be desired in the Cessna category. It is a great aircraft dont get me wrong, but the closest thing that Ive ever seen coming to a Beaver/Otter replacement was either the Helio (not really replacement but a similiar aircraft in performance) or that thing called the "Sherpa" which was like a super cub derived animal that i think had 8 seats built by a guy in i think Washington. I read about it in mayeb Mountain Flying or some magazine (1999/2000 area?). Anywho anyone got more info on that beast thatd be much appreciated. Ciao and keep the blue side up!

ATCT
Trikes are for kids!
 
WrenchBender
Posts: 1662
Joined: Wed Feb 04, 2004 5:59 am

RE: Effectiveness Of Dash 7 Spoilers + Engine Reverse?

Wed Sep 01, 2004 9:50 am

As DHC no longer really exists, now part of the Bombardier group. I can't foresee a dash 9 (DHC-9) unless they breed a CRJ with a Q400 and get a STOL-RJ (wait a minute, isn't that a BAE 146 ?) the others that are now part of Bombardier are Shorts (skyvan) and Canadair (amphibs). The Canadair division is doing well with the amphibs, but the 415T is way to specialized to be considered a bush plane. Therefore owning most of their own competition I cant see a next generation bush plane coming out of Bombardier as long as they stay comitted to the CRJ and the Q400.
The demand in northern Canada and Alaska will always be for true bush planes, something that will operate on wheels/skis/floats from -40 to +30 (celsius) the closest competitor appears to be rotary wing A/C but they have range and temperature problems in direct comparison to bush planes. I have yet to see a Cessna Caravan on skis and the floats available are not the sturdiest things to put on an A/C.

WrenchBender

http://www.airtindi.com/
http://www.arcticsunwest.com/
http://www.arcticdata.ca/~adlairzf/
http://www.buffaloairways.com/ not really bush planes but a great site


Edited to add links to operators in Yellowknife NWT

[Edited 2004-09-01 03:06:03]

[Edited 2004-09-01 03:08:05]
Silly Pilot, Tricks are for kids.......
 
sllevin
Posts: 3312
Joined: Wed Jan 30, 2002 1:57 pm

RE: Effectiveness Of Dash 7 Spoilers + Engine Reve

Wed Sep 01, 2004 2:08 pm

It was less than "thinking STOL" than a failed "thinking ahead" idea.

The Dash-7 was designed around the idea of small, short "city centre" airports that would couple both noise and STOL issues. Toronto City airport and London City were the initial targets -- in fact, until the expansion at LCY I'm fairly sure only Dash-7's couple operate from there.

However, the idea never really blossomed and no further STOLports were built, at which point the slow speed and extra engines of the Dash-7 were nothing more than liabilities.

Steve

Who is online

Users browsing this forum: Eagle15, Google [Bot] and 9 guests