david b.
Posts: 2894
Joined: Fri Jun 15, 2001 7:18 pm

Dash 8 Gear Location

Sat Jan 25, 2003 12:28 pm

Since the landing gear of a Dash 8 is located very close to the engine, will a uncontained engine failure cause the gears to fail? A explosion could rupture hydraulic lines, electric wiring and other mechanic components?
Teenage-know-it-alls should be shot on sight
 
T prop
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Joined: Tue Apr 03, 2001 4:33 pm

RE: Dash 8 Gear Location

Sat Jan 25, 2003 3:03 pm

I have seen the results of a high pressure turbine disc fracture and release of turbine blades in a Dash 8. The aircraft had just taken off and had reached about 50 feet. The engine was operating at takeoff power setting at the time, so the turbine discs were spinning with maximum rotational energy. All the pieces of the turbine disc and blades were contained. In any case they, and the whole engine, are forward of the gear.

Yes, it is possible that an engine fire or maybe an uncontained failure, which I don't think has ever happened in the PW 100 engine series, could take out hydraulics. In this event there is the alternate gear extension system. The alternate extension system is mechanical it basically opens the gear doors and releases the gear from uplock. The main gear most times will drop to down and locked with out assistance, if not there is a hand pump to finish that job. The nose gear has a separate release handle and it drops with the assistance of gravity and the airstream.

Anyway, The answer to your question is no, an uncontained failure should not stop the gear from being extended.


T prop.
 
ScooterTrash
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RE: Dash 8 Gear Location

Sat Jan 25, 2003 3:26 pm

I agree with T prop.

I have never seen an uncontained failure of a PW120 series engine, and I hope I never do! But, I have a hard time imagining any pieces of the compressors or turbines making it to the landing gear, as they would have to pass through allot of metal and go pretty far aft in the nacelle to do so.

I know of only two fires that have ever burned behind the fire wall on a Dash, one Piedmont airplane and one belonging to Horizon (there may have been others). Both fires resulted in a complete loss of all hydraulic quantity (thats right, #1 and #2 systems!) but the landing gear were lowered and where not compromised in any way... at least until that Horizon airplane hit a jetbridge! Those accidents resulted in a Rudder Isolation Valve Airworthiness Directive to prevent a similar occurance.
 
airplay
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RE: Dash 8 Gear Location

Sun Jan 26, 2003 1:47 am

I think if you have an uncontained engine fire or any sort of explosion in that area, operating the gear is the least of your worries!

 Smile
 
delta-flyer
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RE: Dash 8 Gear Location

Sun Jan 26, 2003 7:37 am

Scooter....just to add to what you said....

In the case of the engine fire behind the firewall and both hydraulics being disabled, the greater problem is maintaining yaw control, as there is no mechanical reversion for the rudder. That's why the rudder isolation mod was mandated by an AD. I was the project engineer on that mod, by the way.

Pete
"In God we trust, everyone else bring data"
 
ScooterTrash
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RE: Dash 8 Gear Location

Sun Jan 26, 2003 7:51 am

Thanks for the good work, Pete.

I have flown that scenario in the sim. With no hydraulics on the airplane, Vmc increases to around 165 knots. That makes it pretty tough to return to the field using any sort of engine power. Both that Piedmont crew and that Horizon crew did a fantastic job of saving a horrible situation.
 
bhill
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RE: Dash 8 Gear Location

Sun Jan 26, 2003 9:32 am

Scootertrash..I'm curious, where did the Horizon failure occur? i.e. Was that the incident about 10 years ago at SEA?

Cheers,

Bob
Carpe Pices
 
ScooterTrash
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RE: Dash 8 Gear Location

Sun Jan 26, 2003 12:20 pm

Bhill:

The Horizon accident I am refering to occured in Seattle in 1988. The aircraft suffered an uncontained engine fire which resulted in a total loss of hydraulic fluid. The aircraft landed (somewhat) under control, but due to the loss of the rudder and nosewheel steering ended up impacting concourse B.



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delta-flyer
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RE: Dash 8 Gear Location

Mon Jan 27, 2003 2:46 am

Scooter,

Thanks....just an additional bit....the mod I worked on only covered the existing fleet at the time of the AD -- around 1998 or so. New -200/300's have a different architecture, as they moved the #2 SPU to the tail with a little auxiliary reservoir in the stbd. armpit to take care of rudder isolation.

Another factor that makes the hydraulic system vulnerable to fires is the aluminum high pressure tubing. Usually it is steel, but the engineers wanted to save weight and could make it structurally sound. But at the time (early 80's) the fire-proof standards were not as high as now. Today, the high pressure tubing would be stainless steel or titanium.

The Dash-8 is still a great airplane, though. You're lucky to be flying it!

Pete
"In God we trust, everyone else bring data"
 
Mr Spaceman
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RE: Dash 8 Gear Location

Mon Jan 27, 2003 6:34 am

Hi guys.

Here's the NTSB's final report on that Horizon Air Dash-8 that crashed during landing in Seattle, WA, back in 1988. Thank God nobody was killed!

Unfortunately there's no "Full Narrative" report (much more detail), attached to the synopsis report.

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001213x25438&key=1

Chris  Smile
"Just a minute while I re-invent myself"
 
ScooterTrash
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RE: Dash 8 Gear Location

Mon Jan 27, 2003 10:15 am

I agree Pete! The Dash is a fabulous airplane. My only complaints are that the -100's are wicked hot in the summer time and the -300 bleed system always gives you a pressure bump when you turn it on, no matter what you try! Other than that, it is a really fun airplane to go to work in!
 
dash8tech
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Joined: Mon Jul 05, 1999 8:40 pm

RE: Dash 8 Gear Location

Tue Jan 28, 2003 2:55 pm

Bugger, Been off the computer all weekend...and missed two good Dash 8 discussions....

If you go here there is the full NTSB report of the Horizon incident...shame I can't promote my company in a bit better way in this thread! :-0

http://amelia.db.erau.edu/reports/ntsb/aar/AAR89-02.pdf

Scooter, have you successfully brought the plane down in the sim in this scenario. I've heard from some of our pilots that many have an extremely difficult time getting it back on the deck.

Cheers!
 
ScooterTrash
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Joined: Thu Aug 02, 2001 10:39 am

RE: Dash 8 Gear Location

Wed Jan 29, 2003 10:59 am

Tech:

Hey I am an honest guy! My success record is 50%! The first time I managed to hit the ground... off airport... with the wings level. Maybe someone would have walked away unless we drove through a gas station or something. The second time I made it. The trick is to keep the airspeed above 165 knots if you have any real power on the good engine. Once you get to where u can turn (and it does turn poorly with no rudder!) toward a runway, you have to reduce the power on the good engine close to flight idle to get Vmc down.

This is not a checkride item. We do it in the sim mostly as a fun exercise. Every pilot, to a man, comes away from the experience holding those pilots who managed the senario in realife in very high regard.
 
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Francoflier
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RE: Dash 8 Gear Location

Wed Jan 29, 2003 11:24 am

hi all.

I don't fly the dash 8, but the F-27, which happen to have exactly the same gear-engine configuration.

We had an uncontained engine failure on take off, just as the wheels entered the bays. A scenario close to the one described by T prop up there, only the engine carter and casing did not contain the pieces...

The port Dart was running at take off power (15000 RPM) and the last turbine disc decided leave us. Probably a crack nobody saw... Anyway one piece flew out first (as it turned out, because on the moment I didn't realise anything else than a strong rattling...) and with the disbalance came the other pieces. They tore everything around up. The fuselage looked as if it had been M-16'd. Some pieces flew into the hull, and out the other side of the plane, avoiding some pax by a few inches... not a pretty sight. I hope I can scan the pics soon and post them here.
Some pieces even had to be extracted from the runway, but the thing is, aft of the gear well bulkhead, everything was intact, it all got out sideways. To our immense pleasure the pneumatic system lowered the gear flawlessly on final. When you've crawled your way to 500 ft and maintaining 110 kt all the way around the pattern with an engine that just won't feather, the last thing you need is a stuck landing gear...

Now thankfully, the F-27's rudder and rudder trim are cable operated, so no problem there...

A sad sight really, when we got off.
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
dash8tech
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RE: Dash 8 Gear Location

Wed Jan 29, 2003 3:22 pm

Thanks Scooter, from those same pilots I mentioned they've said that the Captain flying good old 819PH during the actual incident can only manage it half the time! (He's still with us too)

Cheers!

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