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CowAnon
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Joined: Fri Nov 03, 2017 12:03 am

AE2100 military designation?

Mon Nov 23, 2020 8:47 pm

Why were/are the engines for the Lockheed C-130J known as the Allison/Rolls-Royce AE2100D3, a commercial model number, when the engines for the original Lockheed C-130 were called by their military designation of T56 (and not the 501-D, which was Allison's commercial model designation)? The U.S. military operates C-130Js, so aren't their engines supposed to have a military designation as well?
 
GalaxyFlyer
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Re: AE2100 military designation?

Mon Nov 23, 2020 9:17 pm

Probably the bureaucracy never got around to renaming it a T-56xxx. Why is the C-5M not the C-5D or E. Why was the TF33 re-engined KC-135s designated the KC-135E while the CFM-powered ones are designated KC-135R? It doesn’t have to make sense.
 
Ozair
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Joined: Mon Jan 31, 2005 8:38 am

Re: AE2100 military designation?

Mon Nov 23, 2020 9:32 pm

CowAnon wrote:
Why were/are the engines for the Lockheed C-130J known as the Allison/Rolls-Royce AE2100D3, a commercial model number, when the engines for the original Lockheed C-130 were called by their military designation of T56 (and not the 501-D, which was Allison's commercial model designation)? The U.S. military operates C-130Js, so aren't their engines supposed to have a military designation as well?

The C-130J development and acquisition was run as a commercial program, perhaps that has something to do with it.
 
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SheikhDjibouti
Posts: 2348
Joined: Sat Sep 30, 2017 4:59 pm

Re: AE2100 military designation?

Tue Nov 24, 2020 12:51 am

CowAnon wrote:
Why were/are the engines for the Lockheed C-130J known as the Allison/Rolls-Royce AE2100D3, a commercial model number, when the engines for the original Lockheed C-130 were called by their military designation of T56 (and not the 501-D, which was Allison's commercial model designation)? The U.S. military operates C-130Js, so aren't their engines supposed to have a military designation as well?

How about turning the question on it's head and asking
"Why did the US Military routinely apply it's own designation to engines that already had a commercial designation?"

In parallel to this, there is plenty of logic behind the 1962 United States Tri-Service aircraft designation system.

That is why the L-382 is referred to as the "C-130", and the Hawker Siddeley Harrier became the "AV-8B". It's logical, re-assuring and consistent. :checkmark:

Are (were) military engine designations modelled the same way? It seems so, up to a point.

I'm guessing that pre 1962 we had stuff like the J47 (J for Jet) and T56 ( T for Turboshaft/Turboprop)
After 1962, the T-series continued, although it now included some fairly arbitrary numbers (e.g. T408, T700).
Meanwhile the Jets went with F100 etc, except there is another series at F401 etc. And in some cases, the same engine is listed in both series. :o
And then as a separate run, Turbofans such as TF-34 etc.

But then we have the GE CF-6 variously given three different military designations TF-39, F103 and F138. :scratchchin:
These inconsistencies do not inspire confidence in quite the same way.

TL:DR I think the USAF is a little more relaxed about engine designations these days. The AE2100 on the C-130J is by no means an isolated example.



GalaxyFlyer wrote:
Why was the TF33 re-engined KC-135s designated the KC-135E while the CFM-powered ones are designated KC-135R?

Whilst I agree that it often doesn't make sense, I'll take a stab at this one.
The first re-engine program was allocated "E" because it fitted nicely in sequence behind the KC-135A, B & D models.
The second re-engine program was much more of a definitive fix, and "R" was a deliberate jump to indicate "Re-engined". Either that, or they didn't fancy "F" for some reason. :lol:
I would fully expect a re-engined B-52H to be designated B-52R, if it ever happens.

[Note; it's all pure guesswork on my part]
 
prebennorholm
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Re: AE2100 military designation?

Tue Nov 24, 2020 4:25 am

SheikhDjibouti wrote:
The second re-engine program was much more of a definitive fix, and "R" was a deliberate jump to indicate "Re-engined". Either that, or they didn't fancy "F" for some reason. :lol:
I would fully expect a re-engined B-52H to be designated B-52R, if it ever happens.

[Note; it's all pure guesswork on my part]

Yeah, could have been good guesswork, but it isn't so. Actually the R suffix was chosen as the next letter in the alphabet.

Just like the C-135C never came in a KC- version, then C-135G, H, J, K, L, M, N, P and Q only came in C-135, EC-135, NC-135 or RC-135 versions. The letters i and O have nerver been popular as suffix presumably in order not to be confused with the digits one and zero.

The F was a little special. 12 KC-135F were made for the French Air Force.

There was also a KC-135T reengined tanker, and the various C-135 versions almost filled the alphabet, the last one being the EC-135Y (C-135Z still missing).
 
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SheikhDjibouti
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Re: AE2100 military designation?

Tue Nov 24, 2020 11:03 pm

prebennorholm wrote:
SheikhDjibouti wrote:
The second re-engine program was much more of a definitive fix, and "R" was a deliberate jump to indicate "Re-engined". Either that, or they didn't fancy "F" for some reason. :lol:
I would fully expect a re-engined B-52H to be designated B-52R, if it ever happens.

[Note; it's all pure guesswork on my part]

Yeah, could have been good guesswork, but it isn't so. Actually the R suffix was chosen as the next letter in the alphabet.

Just like the C-135C never came in a KC- version, then C-135G, H, J, K, L, M, N, P and Q only came in C-135, EC-135, NC-135 or RC-135 versions. The letters i and O have nerver been popular as suffix presumably in order not to be confused with the digits one and zero.

The F was a little special. 12 KC-135F were made for the French Air Force.

There was also a KC-135T reengined tanker, and the various C-135 versions almost filled the alphabet, the last one being the EC-135Y (C-135Z still missing).

A good summary, although you have barely scratched the surface, and you have made two major errors, and an oversight.
But I also admit that my own comment was 50% tongue-in-cheek, so I'll take half the blame. :white:

So, by implication you are saying that because other C-135s with different prefixes (EC-, RC-, NC- etc) have used up all the intervening suffix letters, when the CFM56 program came along, the KC-135 series was obliged to pick up at letter "R". This idea has some merit. But it isn't as simple as that. And it's wrong.

The first problem is that the same suffix letter has also been used more than once across different prefix C-135s.i.e. there have been C-135A, EC-135A, KC-135A, and RC-135A. And in case you figured that was just a pre 1962 issue, in the 1980's we have the KC-135E, despite previous use of this suffix by C-135E, EC-135E and RC-135E.

Then we have some major inconsistencies such as the suffix "S" being used out-of-sequence all the way back in 1961 (the RC-135S entering service before the RC-135A !)

And the biggest humdinger of all; the first "KC-135R" was an RC-135 (with a technically incorrect prefix), and J57 engines (because this was 1963, and the CFM-56 didn't exist yet)

Just look at the mess people get into regarding "KC-135R" 55-3121.
According to various databases it was built as a KC-135A, re-designated JKC-135A, then KC-135R (v1.0 with J57 engines), KC-135T (still with J57 engines, and not carrying JP-7 fuel either), and eventually in 1971 it finally designated as an RC-135T, which is the actual role it had been performing for years.
In 1982 it was re-engined with TF-33 turbofans, except by now it should have been a TC-135x because the SIGINT gear was removed in 1973 and from then on it only served as a training aircraft, with no operational reconnaissance role.
Again, that is just my take on this plane's history, as you will not find all of that written down in any one place. You have to assemble the truth from a variety of sources that only ever get half of it right.


Hence to my mind, they could have used/re-used any letter they wanted for the CFM56 re-engine program, providing that letter wasn't already taken by a valid KC-135 series a/c.

And if they didn't fancy "any letter", why did they choose "R", when "P" was still available, not just for KC-135s, but across the whole range! :o

[I know you claimed above that "P" had been used, but I haven't found one yet. Pics or it never happened! :rotfl: ]
 
prebennorholm
Posts: 7177
Joined: Tue Mar 21, 2000 6:25 am

Re: AE2100 military designation?

Thu Nov 26, 2020 12:37 am

Impressive, Sheikh, what you know about the 135. Tnx!

SheikhDjibouti wrote:
I know you claimed above that "P" had been used, but I haven't found one yet. Pics or it never happened! :rotfl:


There you are. There are more pics at abpic.co.uk and airphotographicinternational.com, so I assume it isn't a typo.
 
rlwynn
Posts: 1535
Joined: Fri Dec 15, 2000 3:35 am

Re: AE2100 military designation?

Thu Nov 26, 2020 8:38 am

They call them what they want. There are no errors or inconsistencies. Also there is no 'problem' with what the planes are designated..

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