Guest

When Turboprops Taxi...

Thu Dec 30, 1999 9:53 am

Is there a particular reason why turboprops often only use one engine when they are taxiing? Is it to save fuel/engine life? Thanks in advance for the help.

--Jacob
 
aca320
Posts: 130
Joined: Mon Aug 17, 2009 3:12 am

RE: When Turboprops Taxi...

Thu Dec 30, 1999 10:16 am

ya I think you've answered your own question.
 
Guest

RE: When Turboprops Taxi...

Thu Dec 30, 1999 10:18 am

They use both! I have never heard and can not imagen them taxing with one. It is very hard to do and is very dangerous!
Iain
 
F27
Posts: 399
Joined: Mon Oct 08, 2001 11:59 pm

RE: When Turboprops Taxi...

Thu Dec 30, 1999 10:31 am

The reason they shut onw down on taxi is when they arrive at the terminal the passengers can disembark immediately. They usually shut down the number one so it is stopped windmilling by the time they are at the terminal
 
aca320
Posts: 130
Joined: Mon Aug 17, 2009 3:12 am

RE: When Turboprops Taxi...

Thu Dec 30, 1999 10:32 am

umm iainhol I dont know what the situation concerning shutting down one engine on turbo-props has been where youv'e worked but here in cdn its quite normal to shut down one of the engines while taxing usually its no1 typically the side apon which passengers leave the a/c and indeed in certain locations up north we don't shut down the other engine (I'm speaking of course on smaller turbo-props dh8-100 b1900 etc that dont have apu) particularly where there is little or no ground support and its -50 with the wind howlin.
 
Starship
Posts: 1038
Joined: Wed Nov 24, 1999 3:26 am

RE: When Turboprops Taxi...

Thu Dec 30, 1999 10:42 am

I was under the impression that the thrust generated by two props spinning was far in excess of what is required for ground ops. In order to preserve brake life, one engine is shut down, as the other generates sufficient thrust for taxiing.

Nick
Behind every "no" is a "yes"
 
Guest

RE: When Turboprops Taxi...

Thu Dec 30, 1999 10:56 am

I have never seen an turbo prop taxi or even stay at the gate with only 1 engine running. I can understand the deplaning part but I thought you where meaning that they taxi and on there before T/O holding short of the runway they start the other engine and T/O.
Iain
 
Guest

RE: When Turboprops Taxi...

Thu Dec 30, 1999 11:06 am

I spend a lot of time flying thru Atlanta, the home to the world's largest airlines in two fields; Commuter - Atlantic Southeast Airlines - and mainline airline - Delta. (in terms of Pax.)

Both Delta mainline services and Atlantic Southeast taxi on one engine either until they get to the taxiway (ie leave the apron) or after they leave the taxiway (ie get to the apron.) Delta Express pioneered the idea for the main airline, the idea being that the cargo doors can be opened if the No. 2 (No.3 on some DL planes) is shut down on approach to the apron. And also it saves on engine-wear and fuel consumption of course....... which means that whichever you taxied on on takeoff, you must not taxi on on landing - so the wear is relatively equal....

On ASA, they always seem to start the No.1 first, so that cargo can be continued to load until the last minute. And on ASA, they do not stop the prop always when deplaning - sometimes it is still windmilling........




DLMD-11.
 
Guest

RE: When Turboprops Taxi...

Thu Dec 30, 1999 11:09 am

Wow! I guess the best explanation would be to allow pax to disembark sooner. I was at IAD today (watching planes), and yes, it was always the number 1 engine which was turned off first.

--Jacob
 
Starship
Posts: 1038
Joined: Wed Nov 24, 1999 3:26 am

RE: When Turboprops Taxi...

Thu Dec 30, 1999 11:30 am

I just hauled out an old flight test on a Piper Cheyenne 400LS with Garrett TPE 331-14A/B engines (same as on a BAe Jetstream 41) and 110 inch Dowty Rotol paddle blade props.

This set up produces so much thrust that at 30% power the aircraft will slide the tyres.

The report states that with post start-up checks complete, it was apparent that the engines produce a high level of residual thrust, even in flight idle, as the aircraft was straining enthusiastically to get going.

Makes sense then that they would shut one engine down, if they were taxing.

Nick
Behind every "no" is a "yes"
 
L1011
Posts: 2141
Joined: Tue May 18, 1999 8:02 am

RE: When Turboprops Taxi...

Thu Dec 30, 1999 2:29 pm

I have seen this a lot in the old days. Four-engined planes usually shut down two engines when taxiing in. And here in Richmond I once saw a United DC-6 and a Piedmont Martin 4-0-4 keep one engine running while disembarking and boarding passengers. They made a very brief stop here and I guess they thought it would save time. The Martin left the #2 engine running and the DC-6 left the #4 engine running.

Bob Bradley
Richmond, VA
Fly Eastern's Golden Falcon DC-7B
 
OH-LGA
Posts: 1253
Joined: Thu Oct 07, 1999 1:42 am

RE: When Turboprops Taxi...

Thu Dec 30, 1999 2:51 pm

I've seen this many times, most recently when I was spotting at a small airport in the Lake Region of Finland (Savonlinna, SVL) last summer and the first time a Flying Enterprise (Swedish airline cooperating w/ Finnair) SF340 (ex-Finnair) landed, the taxi way is max 300 meters. As soon as you could see them coming from the end of the runway (turn around at the ends, concrete pads) only the engine opposite the deplaning side was running. This also happened when a Finnair ATR-72 arrived for my flight to Helsinki, again, number 1 engine off. I saw it and wondered "What the heck?" but never thought much about it until now... i would say mostly it's for efficency, turn around times are 5 min. (NOT KIDDING) on these quick flights.

Moi,
Kai
Head in the clouds... yet feet planted firmly on the ground.
 
Guest

RE: When Turboprops Taxi...- DLMD-11

Sat Jan 01, 2000 6:34 am

Just a little correction - ASA is not the largest commuter airline; American Eagle is.
 
Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: When Turboprops Taxi...

Sat Jan 01, 2000 9:31 am

I have never seen a turboprop taxi or even stay at the gate with only 1 engine running. I can understand the deplaning part but I thought you were meaning that they taxi and before T/O holding short of the runway, they start the other engine and T/O.

Iain


Depending on the operator (some don't like to shut one down or delay the start for aesthetic reasons believe it or not), the left or #1 engine will be delayed on start until a couple of minutes before takeoff, and shut down once clear of all runways taxiing back into the ramp.

Some conditions where you would want both engines running to taxi: a slippery ramp, windy conditions, tight manoeuvring areas, anticipated reverse taxiing, aircraft unserviceabilities (generator, EEC or other engine MEL items).

Some conditions where you would NOT want both engines running, at least until the tug is clear: slippery ramp during engine start - the idle thrust may cause the aircraft to slide forward with brakes on, risking jack-knifing the towbar. Most normal instances where you would want the engine left off involve long taxi distances or number for take-off.

Good question!

Best Regards & HAPPY NEW YEAR!

Buff
 
akelley728
Posts: 1968
Joined: Tue Dec 07, 1999 12:35 pm

RE: When Turboprops Taxi...

Sun Jan 02, 2000 3:00 am

I flew on a CO ATR42 from EWR to BWI and back on 12/29 and yes, the #1 was shut down as soon as we left the runway on both flights.

I've also flown on a CO B1900 and a NW SF340 and if I remember right the #1 was also shut down on the taxiway.
 
TWA717_200
Posts: 1410
Joined: Tue Nov 23, 1999 3:51 am

RE: When Turboprops Taxi...

Sun Jan 02, 2000 4:28 am

Well, I think that the answer is pretty clear. It's to allow passengers to deplane as soon as possible. Having flown on TWE ATR's and J41's, shutting down the number one when clear of the rwy has always been the case. In addition, on really cold days, I have seen the number 2 engine left running during unload and load to maintain cabin heat.
 
Guest

RE: When Turboprops Taxi...

Sun Jan 02, 2000 7:23 am

I was working on a ATR-72 for a couple of years, and we always had #1 shut down during taxiing both after landing and on taxiing TO the runway BEFORE TAKEOFF!
As fas as I know ALL ATR's have the procedure with o´ne engine taxiing to and from RWY, that is better fuel economy and when approaching the terminal to alloow the pax to disembark the aircraft immediately.

I can't answer for the other aircrafts but the ATR's are using this procedure due to economical and passenger comfort reasons.
 
futurepilot2b
Posts: 130
Joined: Tue Nov 23, 1999 1:35 am

RE: When Turboprops Taxi...

Mon Jan 03, 2000 10:58 pm

I have seen that same thing on the TWE J-41. They shut down the number one engine but I have also seen where they just shut down the prop and allow the engine to continue going. This helps with cabin lighting, and air. Other airlines do that also but most shut down #1 after leaving run way.
 
Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: When Turboprops Taxi...

Tue Jan 04, 2000 6:11 am

Some airplanes, the ATR 42 in particular, are able to apply a propeller brake and stop the propeller from rotating while the engine continues to run. The engine then becomes a very expensive APU. This would never be done though on the side of the airplane where passengers walk back and forth. However the brake could still be used to freeze a windmilling propeller.

The P&W turboprops (PT6 and PW100 series') are "free turbines" where the propeller rotates independently of the engine. The Garrett's on the BAe-41 are fixed shaft so cannot be used in a similar APU fashion as on the ATR42.

Best Regards,

Buff
 
User avatar
B737-112
Posts: 829
Joined: Tue Nov 30, 1999 6:01 pm

RE: When Turboprops Taxi...

Tue Jan 04, 2000 3:51 pm

I have been on a Jetstream J31 on a flight from LAX about six months ago, the pilot started the number one engine and taxied to the full length of 25R on just the one. As soon as the Qantas 747-400 in front was told to take position and hold our pilot started number 2. It was on for only a minute or so before we executed the takeoff roll! -Ryan
 
futurepilot2b
Posts: 130
Joined: Tue Nov 23, 1999 1:35 am

BAE J-41

Tue Jan 04, 2000 10:59 pm

Buff,

I think you are incorrect on your Bae 41. I flew on one in June and got a chance to talk to the pilot. I asked him about this issue. He told me that the engine propeller could be shut down while the engine continues to run. He said is runs like an overgrown APU. He shut down the No.1 just as we left the runway. He used No. 2 to get to the gate and then stopped the prop. I watched this from 13C so I watched it carefully. Hope this helps for everybody else.
 
futurepilot2b
Posts: 130
Joined: Tue Nov 23, 1999 1:35 am

Error On BAE J-41

Tue Jan 04, 2000 11:00 pm

I was seated in 8C. Sorry about that.
 
Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: When Turboprops Taxi...

Wed Jan 05, 2000 1:07 am

Hi Futurepilot2b. I hope your handle is an indication that you will be joining the pilot ranks in some time to come!

I flew the BAe41 at Air Atlantic for 2 years prior to coming to CMM. The 5 they had were the first and only '41s in Canada. Even though they've been for sale for over 4 years, the old owner of AAL still can't get rid of them. They are horrible airplanes for passenger service in Canada.

I am not aware of a gear box that would allow what you are saying. That's not to say it doesn't exist. Those Garrett engines though are fixed shaft engines driving the counter-rotatating propellers through a reduction gear box. Our engineers informed us that the RGB's were only detachable from the engines by qualified overhaulers, which they were not. That meant we had to have two built up engines all the time - an expensive set of spares for such a small fleet.

Again, I am not aware of any modification/STC that would allow the prop to be disengaged from the engine. Any Jetstream Corp experts out there?

Best Regards,

Buff
 
futurepilot2b
Posts: 130
Joined: Tue Nov 23, 1999 1:35 am

RE: When Turboprops Taxi...

Wed Jan 05, 2000 1:42 am

Buff,

Is there any possibility that each individual aircraft can have different engines? Just wondering. Maybe that is a possible for the propeller.
 
futurepilot2b
Posts: 130
Joined: Tue Nov 23, 1999 1:35 am

RE: When Turboprops Taxi...

Wed Jan 05, 2000 2:02 am

Buff,

Are AlliedSignal and Garret the same company or do they manufacturer different engines. Thanks!

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