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MrGtheSheepA346
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Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 2:00 pm

Why dome some airlines operate multi-engine types of the same aircraft? Look for example at TK's A330 fleet. They operate every engine type available on the A330. Their A330-300s are equipped with both GE and RR engines and their A330-200s are equipped with GE, PW and RR (Turkish Cargo). Why is that? In terms of commonality (maintenance wise) this doesn't look ideal.
 
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InnsbruckFlyer
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 2:05 pm

UA's 777-200s have different engines. The PMUA 772s have PW4000s, and the PMCO 772s have GE90s.
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TheFlyingDisk
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 2:10 pm

MrGtheSheepA346 wrote:
Why dome some airlines operate multi-engine types of the same aircraft? Look for example at TK's A330 fleet. They operate every engine type available on the A330. Their A330-300s are equipped with both GE and RR engines and their A330-200s are equipped with GE, PW and RR (Turkish Cargo). Why is that? In terms of commonality (maintenance wise) this doesn't look ideal.


In TK's case, it's probably because they bought planes from other airlines as they become available. For example one A332F is bought from MH which operates PW powered A330s.
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DL_Mech
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 2:46 pm

MrGtheSheepA346 wrote:
In terms of commonality (maintenance wise) this doesn't look ideal.


Not really ideal for a small fleet, but if you have large fleets of different engines (think UPS 757s, Delta 767s) it is not much of an issue.
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AirKevin
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 3:24 pm

Mergers would account for some of them. For instance, United was operating 777s and 757s with Pratt & Whitney engines, whereas Continental had GE90s on their 777s and Rolls-Royce engines on their 757s.
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hOMSaR
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 3:39 pm

What airlines switched engine types for new builds of the same basic variant of a plane (i.e. not one where they were forced to switch because a variant was only offered with a particular engine)? I know BA switched from GE to RR for later batches of 777-200ERs (was that due to unhappiness with the performance of their initial batch of GE-powered 777s?). Of course, Emirates switched from GP to RR on the A380, hoping it would be enough to entice them to go for a neo.

Doesn't LH have both PW and LEAP engines on order for the A320neo?
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 3:41 pm

In most cases, it's because part of the fleet was acquired second-hand. However, LH has been ordering their A320-NEO fleet with a mixture of PW and CFM, but in that case, the fleet will be so large that economies of scale kick in well below LH's fleet size and there are some advantages to a mixed fleet (such as if all the PW jets were to be grounded due to some...hypothetical reason).
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sparky35805
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 4:45 pm

Delta ordered both P&W and GE powered 767-300s.
 
amstone17
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 4:53 pm

Mostly you see this from airlines that have a mixed source for their fleets.

Many airlines purchased a set of aircraft, then wanted more but couldn't get any from the manufacturer for any list of reasons, and looked to other sources, picked up what they could.
Some airlines also have a lot of leased aircraft from different lessors or in addition to purchased fleets, and same reason exists.

In terms of maintenance cost, it's not a huge concern as they also have maintenance agreements spread out to the best vendors, or lessors handle their own maintenance and it doesn't affect the airline's operations. In terms of parts, global parts supply networks are so well established that it's easy to service any common engine without too many head aches, and with many big airlines getting work done by 3rd party maintenance providers, parts stores are not an issue.
 
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 5:20 pm

amstone17 wrote:
In terms of maintenance cost, it's not a huge concern as they also have maintenance agreements spread out to the best vendors, or lessors handle their own maintenance and it doesn't affect the airline's operations. In terms of parts, global parts supply networks are so well established that it's easy to service any common engine without too many head aches, and with many big airlines getting work done by 3rd party maintenance providers, parts stores are not an issue.


As power-by-the-hour agreements become more prevalent, the need to have aligned engine options across larger fleets diminishes.
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MrGtheSheepA346
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 9:55 pm

Mergers are an obvious cause indeed. However, in TK's case, the first batch of A330-300s they ordered are RR equipped with later deliveries fitted with GE engines. Any particular reason for this? Is it similar to the reason EK ordered RR engines now since they were unsatisfied with the fuel economics/performance of the GP7200s?
Last edited by MrGtheSheepA346 on Fri Jan 11, 2019 9:57 pm, edited 1 time in total.
 
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MrGtheSheepA346
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Re: Multi-engine type fleet of same aircraft

Fri Jan 11, 2019 9:56 pm

hOMSaR wrote:
What airlines switched engine types for new builds of the same basic variant of a plane (i.e. not one where they were forced to switch because a variant was only offered with a particular engine)? I know BA switched from GE to RR for later batches of 777-200ERs (was that due to unhappiness with the performance of their initial batch of GE-powered 777s?). Of course, Emirates switched from GP to RR on the A380, hoping it would be enough to entice them to go for a neo.

Doesn't LH have both PW and LEAP engines on order for the A320neo?


TK did that as well on their A333s, went from RR to GE
 
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Re: Multi-engine type fleet of same aircraft

Sat Jan 12, 2019 12:57 pm

In DL's case most of the 767 fleet was purchased new. So why the mixed engine types?

With out knowing the financial details we can only guess. The newer build engines from another manufacturer could have achieved performance gains over the original fleet. The acquisition cost could have been better. For DL we don't do power by the hour. We tend to bring that work in house. The second manufacturer could have given us more contract work, or a better deal on that work if we took planes with their engines.
 
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Re: Multi-engine type fleet of same aircraft

Sat Jan 12, 2019 4:37 pm

You hit the answer ... "financial details". Like buying a car, just bigger. "You mean I can get the Hemi for the same price as the small block? Where do I sign?"
 
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Re: Multi-engine type fleet of same aircraft

Sun Jan 13, 2019 2:30 am

As to the cockpit side of it is there any difference to the pilots when switching from, say a Rolls powered 757 to a Pratt model?
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Re: Multi-engine type fleet of same aircraft

Sun Jan 13, 2019 2:59 am

ClipperYankee wrote:
As to the cockpit side of it is there any difference to the pilots when switching from, say a Rolls powered 757 to a Pratt model?


Yes. Rollers use EPR and N1, while Pratts and GEs use N1 only*. So, for example when initially increasing thrust on take-off on a Roller you'd use an EPR reference, while on the others you'd use an N1 reference*.

The N1 reference numbers would vary a bit by engine type. No big deal though.

* And just to add to the mix, RR XWB engine uses % thrust and N1 instead of EPR and N1.
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Re: Multi-engine type fleet of same aircraft

Sun Jan 13, 2019 4:47 am

Starlionblue wrote:
ClipperYankee wrote:
As to the cockpit side of it is there any difference to the pilots when switching from, say a Rolls powered 757 to a Pratt model?


Yes. Rollers use EPR and N1, while Pratts and GEs use N1 only*. So, for example when initially increasing thrust on take-off on a Roller you'd use an EPR reference, while on the others you'd use an N1 reference*.

The N1 reference numbers would vary a bit by engine type. No big deal though.

* And just to add to the mix, RR XWB engine uses % thrust and N1 instead of EPR and N1.


Thank you for that. As for engine start, same switches, same procedures or would you also need to be aware of what's under the wing and adjust accordingly? We talk about jumping from one Airbus or Boeing model to another or from say an A320 to a 321 all the time on the forum but I don't think I've seen much mentioned on engine types.
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Re: Multi-engine type fleet of same aircraft

Sun Jan 13, 2019 6:35 am

ClipperYankee wrote:
Starlionblue wrote:
ClipperYankee wrote:
As to the cockpit side of it is there any difference to the pilots when switching from, say a Rolls powered 757 to a Pratt model?


Yes. Rollers use EPR and N1, while Pratts and GEs use N1 only*. So, for example when initially increasing thrust on take-off on a Roller you'd use an EPR reference, while on the others you'd use an N1 reference*.

The N1 reference numbers would vary a bit by engine type. No big deal though.

* And just to add to the mix, RR XWB engine uses % thrust and N1 instead of EPR and N1.


Thank you for that. As for engine start, same switches, same procedures or would you also need to be aware of what's under the wing and adjust accordingly? We talk about jumping from one Airbus or Boeing model to another or from say an A320 to a 321 all the time on the forum but I don't think I've seen much mentioned on engine types.


It's all FADEC nowadays, so for normal engine start, I don't think there would be any differences. Ignition on, then master on and let the magical tech take care of the rest. If you have to do "manual start" and other non-normal procedures there might be some variations.
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Re: Multi-engine type fleet of same aircraft

Sun Jan 13, 2019 1:10 pm

Dalmd88 wrote:
In DL's case most of the 767 fleet was purchased new. So why the mixed engine types?

With out knowing the financial details we can only guess. The newer build engines from another manufacturer could have achieved performance gains over the original fleet. The acquisition cost could have been better. For DL we don't do power by the hour. We tend to bring that work in house. The second manufacturer could have given us more contract work, or a better deal on that work if we took planes with their engines.


I remember being told years ago it was influenced by ETOPS. The 767 was DL's first ETOPS experience. Apparently the logic for the mixed engine type was a safety net of sorts. If you have a fleet with only one engine type and something happens to change your ETOPS status it effects every plane in that fleet. By having a mixed fleet DL would limit exposure to half the fleet of 767's should something happen on one engine type.

Today all the engine manufacturers put out reliable products so generally fleet commonality wins and mixed fleets are rare on large new aircraft purchases. As said earlier on second hand purchases generally price wins and the airline takes what it can get.

I can't remember a time where it actually paid off having the mixed fleet but I can understand the logic behind it.
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AirKevin
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Re: Multi-engine type fleet of same aircraft

Sun Jan 13, 2019 6:50 pm

Starlionblue wrote:
ClipperYankee wrote:
As to the cockpit side of it is there any difference to the pilots when switching from, say a Rolls powered 757 to a Pratt model?


Yes. Rollers use EPR and N1, while Pratts and GEs use N1 only*. So, for example when initially increasing thrust on take-off on a Roller you'd use an EPR reference, while on the others you'd use an N1 reference*.

The N1 reference numbers would vary a bit by engine type. No big deal though.

* And just to add to the mix, RR XWB engine uses % thrust and N1 instead of EPR and N1.

Not quite. Rolls-Royce and Pratt & Whitney both use EPR and N1, although the EPR values seem to vary between the two. General Electric uses N1 only.
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Re: Multi-engine type fleet of same aircraft

Sun Jan 13, 2019 10:52 pm

AirKevin wrote:
Starlionblue wrote:
ClipperYankee wrote:
As to the cockpit side of it is there any difference to the pilots when switching from, say a Rolls powered 757 to a Pratt model?


Yes. Rollers use EPR and N1, while Pratts and GEs use N1 only*. So, for example when initially increasing thrust on take-off on a Roller you'd use an EPR reference, while on the others you'd use an N1 reference*.

The N1 reference numbers would vary a bit by engine type. No big deal though.

* And just to add to the mix, RR XWB engine uses % thrust and N1 instead of EPR and N1.

Not quite. Rolls-Royce and Pratt & Whitney both use EPR and N1, although the EPR values seem to vary between the two. General Electric uses N1 only.


Oops. I stand corrected.
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Re: Multi-engine type fleet of same aircraft

Mon Jan 14, 2019 1:03 am

Starlionblue wrote:
AirKevin wrote:
Starlionblue wrote:

Yes. Rollers use EPR and N1, while Pratts and GEs use N1 only*. So, for example when initially increasing thrust on take-off on a Roller you'd use an EPR reference, while on the others you'd use an N1 reference*.

The N1 reference numbers would vary a bit by engine type. No big deal though.

* And just to add to the mix, RR XWB engine uses % thrust and N1 instead of EPR and N1.

Not quite. Rolls-Royce and Pratt & Whitney both use EPR and N1, although the EPR values seem to vary between the two. General Electric uses N1 only.


Oops. I stand corrected.

You do still have a point in that there are differences in the two engines. Rolls-Royce engines would have N3, whereas neither Pratt & Whitney nor General Electric engines have N3, though General Electric would be irrelevant for the 757 since there are no General Electric engines on the 757.
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vhqpa
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Re: Multi-engine type fleet of same aircraft

Mon Jan 14, 2019 3:03 am

Qantas is another airline which has operated mixed engine fleets.

Their 767-200ERs were JT9D powered. The 767-300ERs from their own order were CF6-80 powered. They later operated ex BA 767-300ERs which were RB211 powered. They operated all three subfleets concurrently from about 2000-2005.

Also their first 17 747-200s were JT9D powered as that was the only option when the initial order was placed. Then they switched to the RB211 for the final 5 747-200s, -300s, -SPs and -400s. During the Asian financial crisis in the late 90s they took 3 secondhand -400s powered by CF6-80. Then for the -400ER they chose the CF6-80. As far as I know they never operated all three engines concurrently only a PW/RR and RR/GE combo.

Other instances that come to mind (excluding additional subtypes accquired in mergers)

- DL operare both PW/GE powered A330s
- LH operate CFM powered A319/A320 but IAE A321
- AA ordered CFM A319 and IAE A321 but ended up with a mix of CFM/IAE across the A32S fleet though the US merger which itself had a mixed A32S fleet from the HP merger.
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Re: Multi-engine type fleet of same aircraft

Mon Jan 14, 2019 3:09 am

vhqpa wrote:
Qantas is another airline which has operated mixed engine fleets.

Their 767-200ERs were JT9D powered. The 767-300ERs from their own order were CF6-80 powered. They later operated ex BA 767-300ERs which were RB211 powered. They operated all three subfleets concurrently from about 2000-2005.

Also their first 17 747-200s were JT9D powered as that was the only option when the initial order was placed. Then they switched to the RB211 for the final 5 747-200s, -300s, -SPs and -400s. During the Asian financial crisis in the late 90s they took 3 secondhand -400s powered by CF6-80. Then for the -400ER they chose the CF6-80. As far as I know they never operated all three engines concurrently only a PW/RR and RR/GE combo.

Other instances that come to mind (excluding additional subtypes accquired in mergers)

- DL operare both PW/GE powered A330s
- LH operate CFM powered A319/A320 but IAE A321
- AA ordered CFM A319 and IAE A321 but ended up with a mix of CFM/IAE across the A32S fleet though the US merger which itself had a mixed A32S fleet from the HP merger.


Not uncommon, and not a major issue typically. The CX freighter fleet used to be a bit of a hodgepodge, with 747-412BCFs, 747-467FSCDs and 747-467Fs mounting RB211s, 747-400ERF with Pratt 4062s, and finally 747-8Fs with GEnx. A bit simpler nowadays with just the ERFs and the 8Fs remaining.

On the passenger side, the 777s are mix of 777-300ER with GE90s and other marks with Trents.
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strfyr51
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Re: Multi-engine type fleet of same aircraft

Mon Jan 14, 2019 5:22 am

DL_Mech wrote:
MrGtheSheepA346 wrote:
In terms of commonality (maintenance wise) this doesn't look ideal.


Not really ideal for a small fleet, but if you have large fleets of different engines (think UPS 757s, Delta 767s) it is not much of an issue.

it really depends on If you're doing the Engine Overhauls or flying Power by the Hour where someone Else is doing the Overhauls. Oher than that? The Airline would have to manage their own Spares of which many are surprisingly similar.
 
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Re: Multi-engine type fleet of same aircraft

Mon Jan 14, 2019 3:26 pm

One more to add is that in some cases, you don't get a choice. The airlines that started off with the 777-200ER may have selected one engine manufacturer, and when they got either the 777-200LR or the -300ER, they didn't have a choice. Delta, American, and Singapore got their 777-200ERs with Rolls-Royce engines. I think All Nippon got theirs with Pratt & Whitney engines. Once they got the -200LR (Delta) and the -300ER (the rest), their only option was the GE90.
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Re: Multi-engine type fleet of same aircraft

Mon Jan 14, 2019 5:19 pm

Im pretty sure the AA 320 family order from 2011 spilt engine manufacturers between the 319 (CFM) and 321 (IAE)
 
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Re: Multi-engine type fleet of same aircraft

Mon Jan 14, 2019 5:57 pm

LH and AA went with the IAE 321 and CFM on the smaller ones because those engines made sense for those respective frames (higher thrust/efficiency IAE, lower MX CFM if flown at lower thrust levels).

NZ was another one with mixed RR and GE 744s.

Delta sort of inherited the PW A333s from NW, and then bought GE later (822NW-831NW) as part of a bundle with the CFM A321s.
 
ELBOB
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Re: Multi-engine type fleet of same aircraft

Wed Jan 16, 2019 10:17 am

The Thai situation isn't particularly surprising when you look at the state of their air forces. A hodge-podge of overlapping types acquired on one-off contracts with no concern for commonality or sustenance. When they can no longer sustain a type it is parked and another type bought in its place. Do they really need Alpha Jets and L-39s, or F-16s and Gripens, all at the same time? Of course not but there's no accountability for poor decisions.

Thus likewise at the state airline.
 
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SheikhDjibouti
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Re: Multi-engine type fleet of same aircraft

Wed Jan 16, 2019 12:10 pm

ELBOB wrote:
The Thai situation isn't particularly surprising when you look at the state of their air forces. A hodge-podge of overlapping types acquired on one-off contracts with no concern for commonality or sustenance. Of course not but there's no accountability for poor decisions.

Thus likewise at the state airline.

Civil or military, if the purchasing officer is "persuaded", he will take the best offer in front of him, and not worry about maintenance costs further down the line. All he wants is a new car, some trinkets for the girlfriend, and a holiday for the wife & kids, all expenses paid (cough).

Historically there have been other airlines that enjoyed a variety of engine maintenance problems on the same type.
e.g.
AC; DC-8-43 (RR), DC-8-50 (P&W), (also DC-8-60/70 (P&W, later CFM56s)
AZ; DC-8-43 (RR); DC-8-62 (P&W)
BOAC; B707-336 (P&W); B707-436 (RR)
LH - as BOAC; see photo below
In fact all five operators of the -400 series (BA, LH, AI, EL Al, & Varig) operated a mix of P&W and RR engines
Likewise all three operators of RR powered DC-8-40 series (AC, AZ, and Canadian Pacific, with their supersonic CF-CPG)

These classic photos show a LH 707-330 (P&W) in front of a -430 (RR), and CP Air's record-breaking DC-8-43
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Re: Multi-engine type fleet of same aircraft

Wed Jan 16, 2019 1:59 pm

SheikhDjibouti wrote:
Civil or military, if the purchasing officer is "persuaded", he will take the best offer in front of him, and not worry about maintenance costs further down the line. All he wants is a new car, some trinkets for the girlfriend, and a holiday for the wife & kids, all expenses paid (cough).

It is interesting to note, that when selecting the DC-8, Trans-Canada Air Lines chose the RR Conway. At the time, the vast majority of their aircraft had RR engines. DC-4M, Viscount and the soon to be delivered Vanguard. However RR was paying TCA "never be sorry" payments for the maintenance difference costs of the Merlins over the PW2800s on the DC-6 that TCA wanted. I am sure that "good will" was returned.

When TCA selected the DC-8-54JT with PW engines, the government pushed them to buy the CL-44 instead (with RR Tynes) but they held firm!

However with the DC-8, they never operated more than two engine types at a time. By the time the DC-8-70s were converted, the -43s had already been retired.

A few decades later though,. AC found intself with both GE and PW powered 767-300s and 747-400s!
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Re: Multi-engine type fleet of same aircraft

Wed Jan 16, 2019 10:43 pm

Starlionblue wrote:
vhqpa wrote:
Qantas is another airline which has operated mixed engine fleets.

Their 767-200ERs were JT9D powered. The 767-300ERs from their own order were CF6-80 powered. They later operated ex BA 767-300ERs which were RB211 powered. They operated all three subfleets concurrently from about 2000-2005.

Also their first 17 747-200s were JT9D powered as that was the only option when the initial order was placed. Then they switched to the RB211 for the final 5 747-200s, -300s, -SPs and -400s. During the Asian financial crisis in the late 90s they took 3 secondhand -400s powered by CF6-80. Then for the -400ER they chose the CF6-80. As far as I know they never operated all three engines concurrently only a PW/RR and RR/GE combo.

Other instances that come to mind (excluding additional subtypes accquired in mergers)

- DL operare both PW/GE powered A330s
- LH operate CFM powered A319/A320 but IAE A321
- AA ordered CFM A319 and IAE A321 but ended up with a mix of CFM/IAE across the A32S fleet though the US merger which itself had a mixed A32S fleet from the HP merger.


Not uncommon, and not a major issue typically. The CX freighter fleet used to be a bit of a hodgepodge, with 747-412BCFs, 747-467FSCDs and 747-467Fs mounting RB211s, 747-400ERF with Pratt 4062s, and finally 747-8Fs with GEnx. A bit simpler nowadays with just the ERFs and the 8Fs remaining.

On the passenger side, the 777s are mix of 777-300ER with GE90s and other marks with Trents.

The -412BCFs had the PW4056 to add to the mix, although the 62 is just a thrust bump.
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LH707330
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Re: Multi-engine type fleet of same aircraft

Wed Jan 16, 2019 11:35 pm

All the 707 and DC-8 customers who went from RR to PW did so because the JT3D offered a ~6% fuel burn improvement over the Conway, and on the 320B also an aero cleanup and more MTOW. That's why they only sold 37 707-400s.
 
Okcflyer
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Re: Multi-engine type fleet of same aircraft

Thu Jan 17, 2019 3:37 am

Delta’s first order of A321 are CFM56 powered and without auxiliary tanks (unable to do TCON). Their follow up orders are IAE powered and with aux tanks (TCON capable). In their case, fleet size of both is high enough that additional commonality synergies are minimal.

UA is bringing in several CFM powered A320’s next year when every other A319/A320 is IAE powered.

For traditional hub and spoke airlines, the fleet size for synergy is fairly small. Usually around 20.

However, for low cost carriers, fleet commonality is far more important as they typically don’t use a hub and spoke model. For example, Southwest’s network model relies on a near universial fleet due to their thousand-plus unique city pair combinations.
 
strfyr51
Posts: 3394
Joined: Tue Apr 10, 2012 5:04 pm

Re: Multi-engine type fleet of same aircraft

Thu Jan 17, 2019 6:47 am

InnsbruckFlyer wrote:
UA's 777-200s have different engines. The PMUA 772s have PW4000s, and the PMCO 772s have GE90s.

the PMCO 777's are Years newer than the PMUA 777's. Before Boeing sole sourced the Engine,
 
SXDFC
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Re: Multi-engine type fleet of same aircraft

Mon Jan 21, 2019 9:39 am

Okcflyer wrote:
Delta’s first order of A321 are CFM56 powered and without auxiliary tanks (unable to do TCON). Their follow up orders are IAE powered and with aux tanks


Delta is getting IAE A321s?
 
Okcflyer
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Re: Multi-engine type fleet of same aircraft

Mon Jan 21, 2019 2:04 pm

SXDFC wrote:
Okcflyer wrote:
Delta’s first order of A321 are CFM56 powered and without auxiliary tanks (unable to do TCON). Their follow up orders are IAE powered and with aux tanks


Delta is getting IAE A321s?


Apparently not. My apologies. I went to get a source link for you and discovered ... not sure what happened other than my memory for a year plus has been off on this ... but all will be CFM 5B.

Deepest apologies. Thanks for challenging
 
slcguy
Posts: 275
Joined: Wed Jul 09, 2008 12:09 pm

Re: Multi-engine type fleet of same aircraft

Tue Jan 22, 2019 3:23 pm

UPS with their fleet of B757-200PF is a good example. All aircraft were bought as new builds from Boeing, the first half of the fleet (around 40) were PW powered. The second half (around 35) were RR. I don't have time to check the exact numbers on the fleet sizes but you can look it up if interested. Not sure why they switched from PW to RR midway in delivery of the fleet.
 
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Channex757
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Re: Multi-engine type fleet of same aircraft

Thu Jan 24, 2019 11:21 pm

Lufthansa is about to start deliveries of their next batch of NEOs with a new engine. This means they will have the CFM56 on the A319/320, the V2533 on the A321, Pratt on the A320NEO, and the LEAP on the next tranche of NEOs including the A321NEO.

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