Hotel mode operation on ATRs

[SubsonicMortal]

I am fairly new on the ATR as a fisrt officer and have been wondering about the hotel mode operation on the number two engine.

For those not familiar with ATR hotel mode, it's ATRs version of an APU. The prop is stopped through a prop brake giving full advantage of AC environmental services available.

My question is: Since the engine is running in idle power the ITT on that engine reaches around 485 C with bleed valves off and around 530 C on some of our fleet aircraft with bleed valves on. The aircraft are all cargo mods so we often operate at night and it is often neccesary to run hotel mode for extended periods on the ground while the aircraft is offloaded and then reloaded. I am wondering if those temperatures are detrimental to the engine life since the hot gases are directly expelled onto the stator blades and the stopped turbine section. The only limitation that the ATR FCOM states regarding hotel mode operation is a max ITT of 785 C.

Since there's a debate amongst our aircrew regarding this issue, I would be grateful for any info.

[Captain Stable]

No problem. The engine is still operating. The gust lock ensures you cannot put power on the engine. The HP turbine blades are cooled.

Note that you do NOT have full AC power. ACW is provided from the propeller reduction gearbox and is only available when either prop is unfeathered (on both sides via the AC BTC).

Max ITT in H mode is 715 deg C in my copy of the FCOM 2.01.04 P1.

[Empty Cruise]

C'mon, C.S. :)

You can put a little power on the engine (6-7 deg. PLA, methinks) up to the gust lock stop. V. efficient for opening the HP bleed to get the most out of selecting the aircon to HI FLOW. :p

Hotel mode operation tends to be detrimental only to 1) ground crew comfort 2) crew inside the aircraft if wind is quartering from the rear 3) paint job on aft part of nacelle 4) pilots ego if you forget the max. tailwind component :(

Brgds,
Empty

[False Capture]

Been a while since I've flown an ATR so the following could be out-of-date and full of bad 'hotel mode' memories.:uhoh:

The main issue regarding Hotel Mode is the red NAC OVHT (nacelle overheat) and associated CCAS master warning which requires the immediate shutdown of the no.2 engine. This is due to an overheat detector in the right nacelle - the concern being the damage you can do to the nacelle and not the engine. When you next get an NAC OVHT warning have a look at the ITT, I seem to remember the ITT being nowhere near the limit of 785 C.

In CityFlyer I don't remember any pilots being concerned about the detrimental effect of Hotel Mode on the engine due to high ITT. The main concern was with 'melting the plastic nacelle', to this effect our SOP was to always have a pilot in the flight-deck when No.2 was running in Hotel Mode.

This overheat warning usually occured with a tailwind, but it would also occur on calm days with little/no wind. A few times I had an NAC OVHT whilst waiting at the hold for take-off with both engines and propellers rotating - increasing the power on no. 2 engine cured the warning. Sometimes we'd briefly get the warning with selection of reverse thrust after landing, fortunately this would only last a second or so.

Enjoy the ATR, it's a great introduction to airline flying.:ok:

[ZFT]

Captain Stable

I think Max ITT in H mode is 715 deg C for PW127 whereas I think he was referring to PW121 which is 785 deg C

I stand to be corrected though

[SubsonicMortal]

Yes in my FCOM manuals the max ITT for Hotel mode is given as 785 C. We operate the 300 and 320 models with PW120 & 121 engines.

The argument of some captains is that the stator blades and turbine section is cooled unevenly and therefore not good for the life of the engine. Im sure PW would have stated a limitation other than max ITT if elongated hotel operation would be detrimental to the life of the engine.


Happy flying. Cheers.

:ok:

[Empty Cruise]

Even if it was detrimental to engine life, and you refrained from using hotel mode very often - the engine inspection/overhaul schedule would still be determined by cycles & flighthours (methinks:confused: ). If there had been any evidence whatsoever that excessive H-mode had increased wear & stress on the engine once the nominal inspection interval came up, I'm fairly confident PW/ATR would have been quick to ammend the FCOM.

In other words, same intervals = same maintenance cost per flighthour/cycle + no excessive wear = same component cost per inspection. This - in my limited vocabulary - sounds as though there is absolutely no cost savings to be had by NOT using hotel mode, whereas yield may drop when passengers refuse to fly with somebody offering a too hot or cold cabin for comfort when boarding. Of course you could use ground conditioners or heathers, but unless your airline has its own equipment, it is normally very expensive to rent from the airport (if available at all).

If company not happy with H-mode, should have considered the Dash 8 instead, since it comes with an APU :p

Brgds,
Empty

[SubsonicMortal]

Empty Cruise - very valid argument. Didn't think of it that way. Next time when the debate comes up again I'll mention that as it makes perfect sense.

The other debate is that the company does not want us to engage the prop brake while engine number two is still running. SOPs order us to shut the engine down normally and then to engage the prop brake with the auxilary hydraulic pump. This all to save wear and tear on the brake assembly. In my view this draws quite a bit of power from the battery as the pump runs for 30secs on battery power. This in turn causes the first engine to start hotter than normally.

Anyway, so much for meat and potatoes. Thanks for your input.

[EFP058]

Other than flying one as SLF every now and then I am utterly unfamiliar with the ATR, so please excuse me if this is a stupid question. I was wondering if you guys could tell me how exactly this prop brake works. Is it some kind of mechanical system, or is it a friction brake or something totally different altogether?

How does the ground crew feel about it? I for one would feel somewhat uncomfortable being around a running engine with an engaged propbrake. Is it regarded as if it were a running prop (read: steer well clear of it) or do groundcrew work in that area nevertheless?

[Jagbag]

The right side has to be clear for hotel mode operation (its only on no 2 engine). So no work even though the prop is not moving.

It doesnt necessarily cause any significant damage other than what occurs due normal operation (wear and tear).

It is a great help in hot climates.

Happy Flying!

[farqueue]

Subsonic, does this then add to the engine cycle count? Trashing the prop brake would seem to be a better idea than a hot start or having to rebuild the hot end.

[Empty Cruise]

@ EFP058: It's a hydro-mechanical friction locking device. It uses blue system hydraulic pressure (same as flaps, nosewheel steering, spoilers) to lock and unlock. It will only engage if the following conditions are met: Blue sys press 2900 PSI or above, gust lock engaged, a/c on ground and condition lever (fuel/propeller control) no. 2 in feather OR fuel shut off.

As for ground crew working around the engine - well, it can TECHNICALLY be treated as an APU, but as all things devised by the human mind it can fail. So except from connecting/disconnecting the GPU, no work will be performed on the righthand side while in H-mode.

On a curious note, the FCOM allows refueling with the engine in H-mode :} Again, the difference btw what's legal and what's smart... :D

Subsonic, you don't use GPU? On most airports where you fly regularily, you should be able to negotiate a handling contract where, say, first 30 min GPU use is included in basic handling fee. This will save a lot of wear on the battery + the engine. Plus it will allow pax to deplane without either having to listen to eng. 2 running or boarding with only MIN CAB LT :suspect:

Brgds,
Empty

[SubsonicMortal]

Hi EC -

All the airports we fly into except our home base, does not have GPU facilities. We operate in West Africa where such an item is a luxury. As for pax comfort, luckily we don't have to worry about that as all the flying is cargo hauling.

Farque - As far as I know running hotel mode does not count toward an engine cycle.

We use hotel mode quite extensively but I've never seen an engineer come close to the engine when running it in Hmode. They stay rather far away but I suppose that is mainly due to the noise that Hmode makes. It is incredibly loud.

Happy flying!

[Captain Stable]

Subsonic, shutting down Eng #2, then engaging prop brake then restarting is a total nonsense. The aircraft is designed to engage the prop brake with the engine running. That's the whole point of it. Not only are they increasing wear and tear on the battery and the igniters, and increasing the number of start cycles which also in turn increases their maintenance costs, they are massively increasing wear and tear on the Aux Hyd pump, which is only a small unit, and reducing its life considerably.

You should suggest that they operate the aircraft as ATR intended. If they don't understand any area of operation, perhaps they should speak to a design engineer @ TLS.

I've also heard a lot of nonsense in the past about working aft the exhaust with #2 in H mode. The noise is comparable to the APU of a 737, the engine is not large, and unless you stand right under the jetpipe, you'll have to try very hard to get burned by exhaust. Working by door #2R is not a problem.

[SubsonicMortal]

Hi Capt. Stable

What you're saying makes complete sense. I think I'll have a chat to our maint. dept.

Thanks and happy flying.

Cheers

[LEM]

I've never seen so many people trying to reinvent the wheel as when I was on the ATR...

[SubsonicMortal]

What are you actually saying LEM?

[LEM]

There seems to be a tendency for silly procedures to be developed on that aircraft, like the one you describe to avoid prop brake wear...:rolleyes:

[SubsonicMortal]

I agree with you. It's best to operate the aircraft exactly like the manufacturer intended for it to be operated.

Another procedure our company wants us to employ is to limit the ITTs in the climb to 740 c max. This is all good and well but it often means our actual torque is lower than the pointers of the FDAU torque bugs. This means the aircraft takes longer to climb to the cruise altitude at a higher operating temperature which in my view, adds more wear and tear over time than to just climb at the torque the FDAU bugs "suggest".

[LEM]

Thanks for making me laugh, SubsonicMortal, that reminds me, as I said, my beginnings, and all the various geniuses in action I've witnessed! :yuk:

;)