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killairbus

5th engine doesn't increase ZFW.

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I was wondering how difficult would it be to source some documents to get an idea of how heavy a spare engine on the RR 400 weighs and if PMDG had  a verifiable source would they consider adding it in the next update? 

-Angelo Busato

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Angelo Busato

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2 hours ago, killairbus said:

I was wondering how difficult would it be to source some documents to get an idea of how heavy a spare engine on the RR 400 weighs and if PMDG had  a verifiable source would they consider adding it in the next update? 

-Angelo Busato

Unfortunately, there doesn't appear to be that much information available in the public domain on spare engine carriage, probably due to the fact that it is a relatively rare procedure these days.  The ZFW is affected, but only so far as the weight of the extra engine has the potential to reduce the available payload.  The actual ZFW is a variable anyway and it will depend on the configuration and loading of each aircraft (i.e. configuration, No of pax, freight etc), so the maximum ZFW is not the only limiting factor here. 

Each RR engine weighs approximately 4 tonnes, but as a pilot we don't really need to know that.  What we do need to know about is how carrying a fifth pod will affect the aircraft's performance and handling charactersitics.  Fortunately for us, when the Spare Engine is selected in the QOTS II the FMC will automatically provide all of the necessary additional fuel burn, speed and operating altitude data.  The max TOW and LDG weights are reduced (367.4Kgs & 276.7Kgs respectively) and it will be necessary to adjust the trim settings slightly to compensate for the additional drag and weight of the spare engine.  Other than that and the slight buffet this engine causes there isn't much more to it! 

Rolls Royce engines are very reliable and each one is constantly monitored in real time for any signs of a potential fault developing; so much so that if one engine does fail in flight and it has to be removed to fix it (due to a severe bird strike for example) then the aircraft might be flown without passengers by a specially qualified crew on the three remaining engines to the airline's maintenance facility.

 

Edited by berts
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Bertie Goddard

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On 12/16/2018 at 7:23 AM, berts said:

Unfortunately, there doesn't appear to be that much information available in the public domain on spare engine carriage,

But surely one can find out the weight of an engine at least


Yours truly
Boaz Fraizer
Copenhagen, Denmark

Boeing777_Banner_Pilot.jpg

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For takeoff and landing performance determination, the spare engine certified weight of 6,786Kg is used. For loading calculations (possibly airline specific), the spare engine weights and indexes applied in the Flight Management (FM) load planning system are:

 

RB211-524D4 6,537kg

RB211-524G/H series 6,610Kg

RB211-524G-T/H-T series 6,524Kg

 

 

Edited by Qavion2

John H Watson (retired 744/767 Avionics engineer)

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13 hours ago, Qavion2 said:

For takeoff and landing performance determination, the spare engine certified weight of 6,786Kg is used. For loading calculations (possibly airline specific), the spare engine weights and indexes applied in the Flight Management (FM) load planning system are:

 

RB211-524D4 6,537kg

RB211-524G/H series 6,610Kg

RB211-524G-T/H-T series 6,524Kg

 

 

Thanks!

-Angelo Busato


Angelo Busato

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On 12/24/2018 at 10:36 PM, Qavion2 said:

For takeoff and landing performance determination, the spare engine certified weight of 6,786Kg is used. For loading calculations (possibly airline specific), the spare engine weights and indexes applied in the Flight Management (FM) load planning system are:

 

RB211-524D4 6,537kg

RB211-524G/H series 6,610Kg

RB211-524G-T/H-T series 6,524Kg

 

 

I stand corrected on the weight!  Do you know if your weights for the RB211 are for a complete engine or just the 5th podded part under the wing, because I was perhaps mis-informed they weighed around 4 tonnes (i.e. without the FAN assembly)?   


Bertie Goddard

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Bare weight of the RB211-524G/H, according to my manuals is 9,681lbs (4391Kg). I seem to remember earlier discussions on this as to whether this included the reverser assembly. I think reversers are included in the bare weight of a RB211, but not on a GE.

So where does the (huge) extra 5th pod "weight" come from? I guess the mounting strut weight is included, the fairing panel weight, etc. The fan blades are removed, so that should reduce the weight significantly. I guess the weight penalty is based on aerodynamic drag at critical phases.


John H Watson (retired 744/767 Avionics engineer)

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1 hour ago, Qavion2 said:

Bare weight of the RB211-524G/H, according to my manuals is 9,681lbs (4391Kg).

So I wasn't far out after all when I said the RB211 engine weighed around 4 tonnes.  Having a Spare Engine stuck under the wing reduces the Max Takeoff and Landing weights significantly (typical values could be around 367.4 and 276.7 tonnes respectively, depending on the engine type).

1 hour ago, Qavion2 said:

I guess the mounting strut weight is included, the fairing panel weight, etc. The fan blades are removed, so that should reduce the weight significantly.  I guess the weight penalty is based on aerodynamic drag at critical phases.

The fan assembly is normally carried in the Hold on the same aircraft, so in this situation removing and stowing it won't affect the aircraft's total weight as far as the Spare Engine performance calculations are concerned. The Flight Plan and FMC will provide the appropriate fuel requirements, operating altitudes and speeds for the flight, but the aerodynamic drag caused by the fifth pod is definitely noticeable throughout the flight.   


Bertie Goddard

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