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Loran
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Boeing Designation For 'Convertible' And 'Mixed'

Sat Apr 09, 2016 9:34 am

Dear all,

Hope someone can shed some light into the Boeing designators 'C' and 'M'.

Firstly, is my understanding correct as follows:
- C stands for 'Convertible', equipped with the cargo door at the front and can be operated in full pax or full cargo
- M stands for 'Mixed', also named 'Combi'. A divider separates the cargo and pax compartments

If the above is correct, then I am unclear why the Canadian 737-200s are designated 737-200C, although many are operated in a 'Mixed' configuration. I would assume they were built as 'C's but then later converted to 'M's but their designator never changed?

Another tricky example is the single Nepal 757-200 with cargo door.

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Photo © Suparat Chairatprasert



It is mostly listed as 757-200M but I believe it should be a 757-200C in reality (a.net seems to be correct here), because it is operated in full pax configuration. Can someone confirm?

Thanks,
Loran
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Stitch
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RE: Boeing Designation For 'Convertible' And 'Mixed'

Sat Apr 09, 2016 2:25 pm

The 737-200C was the designation for the all cargo model. Boeing offered a 737-200QC ("Quick Change") that could be either all-cargo or all-passenger (the seats were on pallets so they could be rolled on and off as needed). With the 737 Next Generation Family, the "QC" designation was swapped for "C" - the 737-700C Quick Change can be operated either in an all-cargo or all-passenger configuration.

I do not believe Boeing ever offered a factory-built 737 combi model (that could seat freight in front and passengers in back) nor did they offer a freighter model (sans 737-700C). As such, all 737 Classic and Next Generation Combi and Freighter conversions were done aftermarket. So all the 737 Classic and Next Generation "C" combos are aftermarket designations by the conversion companies (737-400C and 737-800C, for example).

As such, I would guess the Canadian 737-200Cs are aftermarket combi conversions of the original 737-200C all-cargo models.

One note, Boeing is considering offering a combi version of the BBJ (based on the 737-700C).

As of 1978, the 747-200B Combi was the designation for the model that had passengers in the front and cargo in the back. The 747-300 and 747-400 versions of this were known as the 747-300M and 747-400M and I believe Boeing retroactively renamed the 747-200B Combi to 747-200M as that is how they now appear on the Boeing historical Orders and Deliveries website.

The 747-200C Convertible was the model that had the reverse - cargo was loaded in the front (via the nose door) and passengers were loaded in the back. It could also be flown in an all-passenger or all-freight configuration as needed.

As for Nepal's 757-200M, was it originally delivered in a mixed freighter plus passenger configuration with a partition between them that was later removed? If so, then it should be a 757-200M. For example, Lufthansa has removed the partition from their remaining 747-400Ms and operate them in an all-passenger configuration now. However, they are still designated 747-400Ms.

To my knowledge, Boeing never offered a Quick Change version of the 757-200, so the 757-200C does not exist as a Boeing designation.

[Edited 2016-04-09 07:31:22]
 
yeelep
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RE: Boeing Designation For 'Convertible' And 'Mixed'

Sat Apr 09, 2016 5:31 pm

Factory 737-200C = Convertible. It can be all passenger, all cargo or a combi(nation) of the two. The seats are attached to the floor by seat tracks, same as a regular passenger plane. Many have been converted to QC spec.

Factory 737-200QC = Quick Change. Same as the 200C except the seats are on pallets and the configuration can be changed very quickly.

Aftermarket 737-300QC = Quick Change. All passenger or cargo, not sure if they can be flown as a combi due to the change in regulations that required a fixed bulkhead between passengers and cargo.

Aftermarket 737-400C = Combi. Fixed bulkhead, permanent combi.

Factory 737-700C = Convertible. All passenger or cargo.

737-200/300/400/700/800F = Freighter.
 
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7BOEING7
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RE: Boeing Designation For 'Convertible' And 'Mixed'

Sat Apr 09, 2016 11:01 pm

Quoting yeelep (Reply 2):
Factory 737-200QC = Quick Change. Same as the 200C except the seats are on pallets and the configuration can be changed very quickly.

Back in the mid 80's MarkAir in Alaska had a couple of these they'd borrowed (?) from Aloha. They'd fly out to King Salmon to with passengers in back, pick up a load of fish and fly back o Anchorage. With less than an hour turn around (hardly ever made it) they'd take the fish out and slide the seats (on pallets) in and off they'd go to Fairbanks and points north. Only issue was when somebody forgot it was in all passenger configuration and loaded the local minor league baseball team and all their equipment in the seats in the back -- the rest of the plane being empty.
 
Viscount724
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RE: Boeing Designation For 'Convertible' And 'Mixed'

Sun Apr 10, 2016 4:21 am

Quoting Loran (Thread starter):
If the above is correct, then I am unclear why the Canadian 737-200s are designated 737-200C, although many are operated in a 'Mixed' configuration. I would assume they were built as 'C's but then later converted to 'M's but their designator never changed?
Quoting Stitch (Reply 1):
I do not believe Boeing ever offered a factory-built 737 combi model (that could seat freight in front and passengers in back)
Quoting Stitch (Reply 1):
As such, I would guess the Canadian 737-200Cs are aftermarket combi conversions of the original 737-200C all-cargo models.

The Canadian 737-200Cs (among others) were delivered as combis. I'm quite certain of that. I can't recall any "conversion" work" that had to be done with those aircraft were delivered. They could be converted from all cargo to all-passenger or a mix thereof in about 1 hour.

I don't think there was ever a pure freighter version of the 737-200 offered. FedEx took delivery of 5 732 combis in 1979 but found them unsuitable and sold them with a year or two.

There was never a 732M or 732F designation by Boeing as far as I recall.
 
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Jetlagged
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RE: Boeing Designation For 'Convertible' And 'Mixed'

Mon Apr 11, 2016 3:53 pm

Quoting Loran (Thread starter):
It is mostly listed as 757-200M but I believe it should be a 757-200C in reality (a.net seems to be correct here), because it is operated in full pax configuration. Can someone confirm?

In Boeing terms a combi is also convertible, it isn't a fixed configuration. 747-200 combis could be flown in all pax configuration. I know SAA did so. The side cargo door in a 747 Combi had electrical heaters for use when in all pax configuration. So that 757 is correctly designated as a combi.

I think the term combi was first applied by Boeing to the 747-200, after the 737-200C was developed. The concept of the convertible came first, then the combi. Aircraft that were originally designated as convertibles would not be retrospectively redesignated as combis, even if functionally they were the same as combis, as those Canadian 737s were..
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Loran
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RE: Boeing Designation For 'Convertible' And 'Mixed'

Fri Apr 15, 2016 11:00 am

Very interesting, thanks everyone for your insights. It seems the nomenclature of Boeing was not as consistent as I thought. As a consequence I may have to change some types in my log.

Quoting Stitch (Reply 1):
As for Nepal's 757-200M, was it originally delivered in a mixed freighter plus passenger configuration with a partition between them that was later removed?

Good question, I don't know.

Quoting Stitch (Reply 1):
To my knowledge, Boeing never offered a Quick Change version of the 757-200, so the 757-200C does not exist as a Boeing designation.

Interesting, as this single 757 seems to be very inconsistent depending on the fleet list you look at. Is it possible to look the original configuration up on the being page? Haven't searched yet but will have a look later.

Quoting yeelep (Reply 2):

Thank you yeelep. I have flown on most the ones you mentioned, except the freighters and -200QC.

Quoting Viscount724 (Reply 4):
There was never a 732M or 732F designation by Boeing as far as I recall.

Interesting, thanks. I flew on some Colombian 737-200s, one of them a 737-200C in all cargo:

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Photo © Andres Dallimonti


And this one seems to be labelled as an 737-200/Adv(F):

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Photo © Juan David Piraquive



So it is to assume the second 737 has an incorrect 'F' designation. I recall the difference between the two was that the 'F' had a fixed bulkhead between the front entry & crew section, whereas the 'C' only had a cargo net separating the front/entry area and cargo section.

Quoting Jetlagged (Reply 5):
In Boeing terms a combi is also convertible, it isn't a fixed configuration. 747-200 combis could be flown in all pax configuration. I know SAA did so. The side cargo door in a 747 Combi had electrical heaters for use when in all pax configuration. So that 757 is correctly designated as a combi.

Makes sense. This means I may have to change EP-MND I flew on to a 747-300(M) versus my current log entry as a 747-300(SCD):

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Photo © Mohammad Shaltookei



Thanks again to everyone.
Regards,
Loran
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yeelep
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RE: Boeing Designation For 'Convertible' And 'Mixed'

Fri Apr 15, 2016 6:03 pm

Quoting Loran (Reply 6):
And this one seems to be labelled as an 737-200/Adv(F):

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Photo © Juan David Piraquive



So it is to assume the second 737 has an incorrect 'F' designation.

That plane has been converted from a passenger version.
 
CanadianNorth
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RE: Boeing Designation For 'Convertible' And 'Mixed'

Mon Apr 18, 2016 8:52 pm

I can't speak for other Boeing airliners, but with regards to the 737 the only official Boeing designation I've come across is C.

Boeing 737-200C: "737-200 Convertible", and offered straight from the factory as such. The idea was you can do full passenger, full freight, or a combination of the two, and "convert" it back and forth as required. Most of the designs and ideas were just a copy and paste from the 707 and 727 Convertible projects. I recall reading that once Boeing got underway with the 737-200C project they also offered a 737-100C but there wasn't much interest so the idea was shelved.

With this set up usually the seats are installed in the seat rails as per normal, and there is a bulkhead that can be installed in several different places depending on what ratio of cargo and passengers you want. There was a version of the 737-200 Convertible that was marketed as the -200QC, or "Quick Change", this is just a regular -200C only with the seats mounted to special pallets so you can load slide and lock (going off of memory here, feel free to correct me anyone) six seat benches at a time instead of carrying up and installing the benches individually. This system eats a chunk of payload due to extra weight but would allow operators to reconfigure on a turn, where as the regular system takes at least a couple of hours for your maintenance team to "convert".

Boeing 737-300C and 737-400C: "Combi". These are aftermarket conversions of a regular 737-300 or 737-400, as far as I know Boeing did not deliver anything other than regular passenger 737-300s and 737-400s from the factory. I've been told there is no 737-500C because the combination of short fuselage and big old CFM hanging out in front of the wing doesn't leave enough room for the standard size cargo door and loading systems to work.

There are three mods you can choose from as far as I can tell. One is a conversion to a pure freighter, one can do either full passenger or full cargo and be converted back and forth all you want, and the other one is a fixed combi. The fixed combi on the 737-300C and 737-400C was developed as a replacement for the 737-200C (at least for routes not requiring the gravel capabilities of the old JT8D powered 737s), however to meet the newer regulations when it was certified (mostly to do with fire) the bulkhead needs to be fully smoke proof among other things. Because of this once it is installed the bulkhead is now pretty well permanent, so during the initial set up you pick your ratio of passengers and cargo on the main deck and that's what you are stuck with. The common setup is about 50/50, three pallets and 60 some odd seats for the -300 and four pallets with 70 ish seats for the -400.

I've never really had anything to do with the 737 NG so I can't really say much about those programs.
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