ATR hotel mode
Thread Starter
Joined: May 2006
Posts: 75
Likes: 0
From: on the move
ATR hotel mode
Why the ATR was designed with that hotel mode vs a light APU ?
To save weight and/or simplify systems ?
I´ve always found that right prop locked quite scary with ground crew/equipment wandering around.
Thanks.
To save weight and/or simplify systems ?
I´ve always found that right prop locked quite scary with ground crew/equipment wandering around.
Thanks.
Joined: May 2000
Posts: 731
Likes: 0
From: Strood, Kent
And it's on the same side that refuelling & baggage loading takes place so that doesn't work very well either.
Five minutes of heat on a cold morning before anyone else turned up is about all it was good for, in my recollection.
Five minutes of heat on a cold morning before anyone else turned up is about all it was good for, in my recollection.
Joined: Dec 2002
Posts: 25
Likes: 0
From: USA
More about the prop brake
The term hotel mode is actually a nautical term. When cruise ships would pull into port, they would disengage the screws from the powerplants so that they could still get electricity to keep the ship powered without turning the screws.
On the ATR, hotel mode refers to the operation of the right engine with the prop brake engaged. The ATR series, having Pratt and Whitney 100-series free-turbine engines, has a multi-disk propeller brake installed on the right propeller's reduction gear box. When it is engaged, the crew can run the right engine without turning the propeller. This supplies DC power and bleed air for the air conditioning. It is hydraulically actuated, electrically controlled, and mechanically locked. It can be engaged with the engine shut down, or with the right propeller spinning in feather. Its logic is designed so that it cannot be engaged in flight. ATR did design it as a substitute for an APU to save weight, complexity, and to minimize DOC. Since every aircraft design decision is a compromise, the prop brake solution does have its limitations.
Hotel mode cannot be used full-time at the gate like a conventional APU. Typically, the ATR cannot be fueled while in hotel mode. Also, most rampers do not care to load bags through the aft service door with a noisy, hot engine running 30 feet or so from them. Even though the prop brake can be a very reliable system, there is always the danger of the brake letting go and the propeller rotating with ground personnel in its vicinity. As someone else said, hotel mode can be tricky in a tailwind. The nacelles of the ATR are primarily composite. It is easy to overheat the right engine nacelle when running in hotel mode with a tailwind, since there is no propeller spinning to move air over the engine nacelle. The right engine nacelle is monitored for overheat. Naturally, this somewhat reduces the flexibility of hotel mode. Also, the engine running in hotel mode (typically at 68%-72% Nh) does not provide very high pressure air to the packs, so it does not cool the aircraft as effectively as an APU that runs around 100% of its rated RPM. In a warm climate, pre-cooling a heat-soaked ATR without passengers becomes neccesary. Airlines that choose to use the prop brake will typically start the right engine with the prop brake on a few minutes prior to departure, disengage it to taxi, and then re-engage the prop brake arriving at the destination and then operate in hotel mode until a GPU is plugged in.
The main maintenance problem with the prop brake is slippage. If the brake disk gets sufficiently worn, the prop can slip and rotate while in hotel mode. Although there is no cockpit indication, it is noticeable from the cockpit. Naturally, this is a dangerous condition for anyone near the right engine. If the prop brake fails, it must either be removed from the aircraft or repaired. Some airlines have had bad luck with this system and have removed the system from their aircraft. The airline I work for now has had good luck, and I believe this is due to the fact that we realize its limitations. We carry very few prop brake deferrals and have very few failures.
I know this was a windy post, but the prop brake is definitely a unique and defining feature of the ATR series. Therefore, I enter my scant knowledge of it into the record.
On the ATR, hotel mode refers to the operation of the right engine with the prop brake engaged. The ATR series, having Pratt and Whitney 100-series free-turbine engines, has a multi-disk propeller brake installed on the right propeller's reduction gear box. When it is engaged, the crew can run the right engine without turning the propeller. This supplies DC power and bleed air for the air conditioning. It is hydraulically actuated, electrically controlled, and mechanically locked. It can be engaged with the engine shut down, or with the right propeller spinning in feather. Its logic is designed so that it cannot be engaged in flight. ATR did design it as a substitute for an APU to save weight, complexity, and to minimize DOC. Since every aircraft design decision is a compromise, the prop brake solution does have its limitations.
Hotel mode cannot be used full-time at the gate like a conventional APU. Typically, the ATR cannot be fueled while in hotel mode. Also, most rampers do not care to load bags through the aft service door with a noisy, hot engine running 30 feet or so from them. Even though the prop brake can be a very reliable system, there is always the danger of the brake letting go and the propeller rotating with ground personnel in its vicinity. As someone else said, hotel mode can be tricky in a tailwind. The nacelles of the ATR are primarily composite. It is easy to overheat the right engine nacelle when running in hotel mode with a tailwind, since there is no propeller spinning to move air over the engine nacelle. The right engine nacelle is monitored for overheat. Naturally, this somewhat reduces the flexibility of hotel mode. Also, the engine running in hotel mode (typically at 68%-72% Nh) does not provide very high pressure air to the packs, so it does not cool the aircraft as effectively as an APU that runs around 100% of its rated RPM. In a warm climate, pre-cooling a heat-soaked ATR without passengers becomes neccesary. Airlines that choose to use the prop brake will typically start the right engine with the prop brake on a few minutes prior to departure, disengage it to taxi, and then re-engage the prop brake arriving at the destination and then operate in hotel mode until a GPU is plugged in.
The main maintenance problem with the prop brake is slippage. If the brake disk gets sufficiently worn, the prop can slip and rotate while in hotel mode. Although there is no cockpit indication, it is noticeable from the cockpit. Naturally, this is a dangerous condition for anyone near the right engine. If the prop brake fails, it must either be removed from the aircraft or repaired. Some airlines have had bad luck with this system and have removed the system from their aircraft. The airline I work for now has had good luck, and I believe this is due to the fact that we realize its limitations. We carry very few prop brake deferrals and have very few failures.
I know this was a windy post, but the prop brake is definitely a unique and defining feature of the ATR series. Therefore, I enter my scant knowledge of it into the record.
Joined: Dec 2003
Posts: 329
Likes: 0
From: Blighty - On secondment
'And it's on the same side that refuelling & baggage loading takes place so that doesn't work very well either.'
The bags are not loaded on the right hand side (as in most airliners) but are loaded on the left hand side and not on the side of the number two engine (in hotel mode).
The bags are not loaded on the right hand side (as in most airliners) but are loaded on the left hand side and not on the side of the number two engine (in hotel mode).
Joined: Apr 2003
Posts: 1,045
Likes: 1
From: North of CDG
Brasilia Captain - You saved me reading the relevant FCOM pages again! 
An advantage of the prop brake is that one doesn't have to ask for ATC start clearance to start No.2 in Hotel mode, since the prop isn't turning. Also, in my outfit at least, we will typically start No.2 in Hotel mode, then disconnect the GPU, then start No.1, release the prop brake, and put both props to MAX RPM prior to taxi (alternatively, we can start both before disconnecting the GPU). Probably saves a bit of time on handling procedures.
NAC OVHT is indeed an issue in a tailwind; you're there minding your own business, when suddenly you get an MW, a CRC and NAC OVHT on the CAP. You can then either:
1/ Release the prop brake to create airflow over the nacelle - not really feasible when waiting for a GPU (but OK if it happens while you're taxying)
2/ Shut down No.2 - but then you're on battery only (unless you want that OFF too)
As with every system, it's OK as long as you know its limitations.
Cheers
An advantage of the prop brake is that one doesn't have to ask for ATC start clearance to start No.2 in Hotel mode, since the prop isn't turning. Also, in my outfit at least, we will typically start No.2 in Hotel mode, then disconnect the GPU, then start No.1, release the prop brake, and put both props to MAX RPM prior to taxi (alternatively, we can start both before disconnecting the GPU). Probably saves a bit of time on handling procedures.
NAC OVHT is indeed an issue in a tailwind; you're there minding your own business, when suddenly you get an MW, a CRC and NAC OVHT on the CAP. You can then either:
1/ Release the prop brake to create airflow over the nacelle - not really feasible when waiting for a GPU (but OK if it happens while you're taxying)
2/ Shut down No.2 - but then you're on battery only (unless you want that OFF too)
As with every system, it's OK as long as you know its limitations.
Cheers
Last edited by FougaMagister; 26th August 2007 at 13:20.
Joined: Aug 2004
Posts: 409
Likes: 0
From: South of the border
a poor mans APU!
With ref to the possible ATR stretch/new model that has been mooted from various sources - will be interesting to see if ATR stick to the prop brake concept or go the full hog and install a proper and usable APU.
Ok being harsh...the prop brake is usable, just have to be aware of its very real limitations.
With ref to the possible ATR stretch/new model that has been mooted from various sources - will be interesting to see if ATR stick to the prop brake concept or go the full hog and install a proper and usable APU.
Ok being harsh...the prop brake is usable, just have to be aware of its very real limitations.
Joined: May 2000
Posts: 731
Likes: 0
From: Strood, Kent
The bags are not loaded on the right hand side (as in most airliners) but are loaded on the left hand side and not on the side of the number two engine (in hotel mode).
According to FCOM 2º part , 2.06.03,pg 2 you can refuel the aircraft with RH engine running in hotel mode.
I always wondered why the exhaust nacelles weren't designed to point upwards as on the Dash 8. I think that would have made hotel mode at least a little bit more user friendly (although the exhaust was quite comforting on a cold and frosty morning).
Thread Starter
Joined: May 2006
Posts: 75
Likes: 0
From: on the move
Dixons,
Is there a new stretched version to come ?
Like the ATR 72-1000 ?
That d be cool but never heard about it.
Let s say a 6 feet extension forward, APU in the back for weight and balance without having to stretch the aft to much for tail strikes. 4500 hp/side or so, 90 pax. another 5o kts TAS, better rate of climb without being to limited in icing.
And then a better range for that higher cruise speeds.
Oh yeah and an oven for hot meals.
I can see a few routes and a fine good plane...
Cheers.
Is there a new stretched version to come ?
Like the ATR 72-1000 ?
That d be cool but never heard about it.
Let s say a 6 feet extension forward, APU in the back for weight and balance without having to stretch the aft to much for tail strikes. 4500 hp/side or so, 90 pax. another 5o kts TAS, better rate of climb without being to limited in icing.
And then a better range for that higher cruise speeds.
Oh yeah and an oven for hot meals.
I can see a few routes and a fine good plane...
Cheers.
Joined: Aug 1999
Posts: 1,050
Likes: 4
From: England
Ah, Beaver, the good old days....
Sprint to the aircraft to try and beat the loaders / refueller / caterer. Crank up Hotel mode for a few minutes to take the chill off before they arrive.
Turn up the chart light on the control yoke, and clamp the headset onto it to warm up the gels. Turn on all the filament tests, close the overboard valve and try to glean half a degree centrigrade from somewhere.
Its almost enough to make me feel nostalgic
pb
Sprint to the aircraft to try and beat the loaders / refueller / caterer. Crank up Hotel mode for a few minutes to take the chill off before they arrive.
Turn up the chart light on the control yoke, and clamp the headset onto it to warm up the gels. Turn on all the filament tests, close the overboard valve and try to glean half a degree centrigrade from somewhere.
Its almost enough to make me feel nostalgic
pb
Joined: Dec 2006
Posts: 69
Likes: 0
From: Desert
Continuing the nostalgia: Look at your IAS and see barely 180kt in cruise, Hear the F/A complaining about cabin temperature,turbulence and ice accretion on FL180/160, the atc asking you if possible to increase the IAS during descent/approach.........
Joined: May 2000
Posts: 731
Likes: 0
From: Strood, Kent
[Thread drift]
Sounds like you're about to go back into flying to me CPB. May I take this opportunity to remind you of some of the drawbacks?..
Four GLA night stops in the past 9 days (two four day tours with 14 sectors per tour) with less than 12 hours rest on all four and the first one of each tour followed by an 11:05 planned duty day (which overran each time although did have a much longer MAN slip after it and before the second GLA).
And the CC are even in a different hotel in both MAN & GLA now too.
Anyway, the old days certainly did have some redeeming features, didin't they?
Have you considered joining Chris F down at Aurigny? Might be able to recapture the magic? Much as I'd love it, the future's in RHS LH for me... Off to the 744 in December. I want my life back too, but have chosen a different solution to you.
[/thread drift]
Er... Oh yeah! ATRs... That stretched version discus2 has dreamed up sounds like a winner to me. The ATR is certainly a good money making machine, whatever it's foibles.
Amazing that they went a whole year without selling one a few years back. Turboprops seem to be back on the agenda again now that fuel is so expensive and curbing air travel is beginning to move up the political agenda.
Sounds like you're about to go back into flying to me CPB. May I take this opportunity to remind you of some of the drawbacks?..
Four GLA night stops in the past 9 days (two four day tours with 14 sectors per tour) with less than 12 hours rest on all four and the first one of each tour followed by an 11:05 planned duty day (which overran each time although did have a much longer MAN slip after it and before the second GLA).
And the CC are even in a different hotel in both MAN & GLA now too.
Anyway, the old days certainly did have some redeeming features, didin't they?
Have you considered joining Chris F down at Aurigny? Might be able to recapture the magic? Much as I'd love it, the future's in RHS LH for me... Off to the 744 in December. I want my life back too, but have chosen a different solution to you.
[/thread drift]
Er... Oh yeah! ATRs... That stretched version discus2 has dreamed up sounds like a winner to me. The ATR is certainly a good money making machine, whatever it's foibles.
Amazing that they went a whole year without selling one a few years back. Turboprops seem to be back on the agenda again now that fuel is so expensive and curbing air travel is beginning to move up the political agenda.
ECON cruise, LR cruise...
Joined: Apr 2002
Posts: 569
Likes: 0
From: MIRSI hold - give or take...
Re. the duct press you get out of Hotel-mode; you are actually allowed (as per FCOM,not to hand so please - don't ask me for a reference) to bring the RH powerlever forward to the gust lock stop to increase Nh and thus airflow.
Of course, this is a very good way of finding out if your prop-brake is worn & prone to slip
...
A lot of the airlines that haven't had much luck with the propbrake are the ones that could not convince their crews the SE taxi is done on no. 2 only
(as in exclusively, every time, but not exceptions, don't even contemplate it etc. etc.).
Of course, this is a very good way of finding out if your prop-brake is worn & prone to slip
...A lot of the airlines that haven't had much luck with the propbrake are the ones that could not convince their crews the SE taxi is done on no. 2 only
(as in exclusively, every time, but not exceptions, don't even contemplate it etc. etc.).
Joined: Dec 2002
Posts: 25
Likes: 0
From: USA
NSR,
Actually, you may or may not get an UNLOCK indication if the prop brake malfunctions. It depends on the type of malfunction.
As I posted earlier, a most common malfunction is slippage. Slippage occurs when the engine is running in hotel mode and the propeller rotates, meaning the prop brake can no longer completely hold the prop in place. If the brake pads themselves are excessively worn, but the prop brake is still in the locked position, the UNLOCK light will not illuminate. The UNLOCK light only 'looks' at prop brake switch position and prop brake position; it does not monitor brake wear.
However, if the prop brake unlocks (meaning the brake assembly itself)without being commanded, you will get an UNLOCK light and the associated CCAS indications.
I hope this clarifies what I posted earlier.
Regards,
BrasiliaCaptain (at least I was a few years ago)
Actually, you may or may not get an UNLOCK indication if the prop brake malfunctions. It depends on the type of malfunction.
As I posted earlier, a most common malfunction is slippage. Slippage occurs when the engine is running in hotel mode and the propeller rotates, meaning the prop brake can no longer completely hold the prop in place. If the brake pads themselves are excessively worn, but the prop brake is still in the locked position, the UNLOCK light will not illuminate. The UNLOCK light only 'looks' at prop brake switch position and prop brake position; it does not monitor brake wear.
However, if the prop brake unlocks (meaning the brake assembly itself)without being commanded, you will get an UNLOCK light and the associated CCAS indications.
I hope this clarifies what I posted earlier.
Regards,
BrasiliaCaptain (at least I was a few years ago)
Joined: May 2006
Posts: 132
Likes: 0
From: EGKB
What abot ATR 42-541 AGV ?
It has "third engine" I guess they mean APU to start up other to and support electronics.
http://lotnictwo.net/doc.php?doc=07040101 ( I know it's in Polish).
It has "third engine" I guess they mean APU to start up other to and support electronics.
http://lotnictwo.net/doc.php?doc=07040101 ( I know it's in Polish).
