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convair880mfan
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Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 12:20 am

For all its merits, sometimes it is hard to get historical data on the Internet. I am wondering why the Boeing 727 wasn't designed around some version of the Pratt and Whitney JT3D engine? A 27 pilot told me he thought the trijet was underpowered. Why not use the Jt3D? Was it a weight issue? Fuel burn economics?

I can't imagine noise was a big issue in those days. But perhaps. Would the JT3D not have worked in the center tail position engine because of the short bypass duct? Would be interested to find out if anyone knows the answer to this?

I know some airlines wanted something that could get in and out of the short runways at La Guardia and have three engines to fly over the Rockies. I imagine that the J3TD engines would have made the 727-100 tail heavy . A center of gravity /weight and balance nightmare?

Thanks in advance for any information.
 
GalaxyFlyer
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 12:45 am

Probably wouldn’t have worked in #2 position, but the real reason was the JT-8 was better, more modern engine. It was based off the J52 used in the A-4 and A-6. True, by today’s standards somewhat underpowered, but it met all the performance requirements despite gaining about 33% in TOGW, a stretch and ever more challenging airports. 72S operated out of DEN, MEX, for example. Tail-mounted engines do make for little room to change engines after the design is frozen.

The 3-engine design was because at the time a twin couldn’t depart without being able to return to field that is, the had to have landing weather to depart. A tri- could declare a departure alternate. That’s changed over the years, but in 1956 was a big limitation in LGA where ILS 04, most often used bad weather, nor’easterly wind had mins of 400’-3/4 mile.
 
convair880mfan
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 1:49 am

Thanks for that information, GalazyFlyer. It makes sense to me.
 
LH707330
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 4:38 am

Even in those days, fuel burn was important: you don't want to burn too much fuel because even if it was free, it still eats into your payload and range numbers. Granted, expensive fuel shifts the priority a bit, but it's not like the designers of the time were not chasing every last % the same exact way they do today.

As GalaxyFlier said, the JT8D was the right engine for the job: anything bigger would have resulted in unnecessary structural weight and hence fuel burn. I'd be curious to see how the early JT8D compared with the mature JT3D-3B in terms of cruise SFC, seems there was a thread on it that suggests the 8 was better, but didn't fully resolve the discussion: viewtopic.php?t=722165

Regarding the thrust levels, pilots always complain about planes being underpowered because it makes them less fun to fly, but as long as there's enough thrust to meet the certification and performance requirement, it works. I'm sure there are former jet jocks who think an empty 757 is underpowered.
 
CRJockey
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 7:09 am

LH707330 wrote:
Regarding the thrust levels, pilots always complain about planes being underpowered because it makes them less fun to fly, but as long as there's enough thrust to meet the certification and performance requirement, it works. I'm sure there are former jet jocks who think an empty 757 is underpowered.


Apart from piston aircraft, I never heard anyone complain about the available power of an aircraft. Fun to fly is a relative term anyway and is mostly during approach and landing, imho, where power is plenty due to the low fuel levels.

After liftoff, well, there is not really much more fun if the aircraft is climbing with 2500 ft/min rather than 1200 ft/min. You are mostly restricted by airspace constraints anyway, so rare occurences where you can fly an empty aircraft unrestricted to high levels. And even then, even with 4000 ft/min climb rate: as soon as the climb is established, yes, your altimeter is racing upwards, but it is not as if you were pressed in your seat like in Top Gun.

Well, my experience anyway.
 
T54A
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 8:48 am

The B727-200 with the JT8D-17 was ok. Those powered by the -15 were a bit lazy getting airborne.
 
VMCA787
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 11:02 am

[quote="T54A"]The B727-200 with the JT8D-17 was ok. Those powered by the -15 were a bit lazy getting airborne.[/quote

Obviously, you have never flown in a 200 with-7 engines!!!
 
T54A
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 11:45 am

VMCA787 wrote:
T54A wrote:
The B727-200 with the JT8D-17 was ok. Those powered by the -15 were a bit lazy getting airborne.[/quote

Obviously, you have never flown in a 200 with-7 engines!!!


Thank heavens not
 
Okcflyer
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 3:20 pm

The later 200-series JT8D's are nearly 20% more efficient than comparable JT3D is. I imagine the early models still have a significant advantage (I'm unsure how much but i wager >10%) but at a lower thrust output.
 
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dennypayne
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Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 4:57 pm

CRJockey wrote:
Apart from piston aircraft, I never heard anyone complain about the available power of an aircraft.


I heard the DC-9 referred to as the “Lead Sled” quite a bit from folks who flew it. I don’t think the 727 was considered a huge improvement.
 
SteelChair
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Aug 25, 2021 5:07 pm

The posts on this thread are really about wing loading and power loading Imho. The 727 and DC9 had small wings, high power loading. Boeing attempted to compensate with huge, complex flaps. There were still some "deep stall" accidents on the 727 IIRC. Neither airplane had enough power imho.

The 757 was better balanced imho. Good wing and power loading. Unfortunately, most of the time it's performance wasn't needed.....that's why airlines quit buying them. A321 NEO and MAX are well balanced amd optimized for routes shorter than 757 mho.

A classic case of a too small wing is the MD11. They tried to compensate with power. I once had a pilot tell me that doing the noise abatement departure at PDX at MTOW would result in stick shaker activation.....yet such operation was approved! The 11 also routinely can't comply with the 250kts below 10,000 feet regulation. Just not enough wing.
 
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Strebav8or
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Re: Why didn't Boeing power the 727 with JT3D engines?

Fri Aug 27, 2021 5:11 pm

And could relate to overall size and weight
JT3D: 53" Diameter, 142" Length, 4600 Pounds (Dry)
JT8D-17: 40" Diameter, 124" Length, 3500 Pounds (Dry)

And speaking from experience....the 727 was a tail heavy bird
 
DeltaMD95
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Re: Why didn't Boeing power the 727 with JT3D engines?

Sun Sep 19, 2021 10:37 pm

SteelChair wrote:

A classic case of a too small wing is the MD11. They tried to compensate with power. I once had a pilot tell me that doing the noise abatement departure at PDX at MTOW would result in stick shaker activation.....yet such operation was approved! The 11 also routinely can't comply with the 250kts below 10,000 feet regulation. Just not enough wing.


Ironically, the wingspan shortcoming has contributed to the MD-11’s longevity as a freighter, given it’s ramp space flexibility for an aircraft of such payload.
 
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tb727
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Re: Why didn't Boeing power the 727 with JT3D engines?

Tue Sep 21, 2021 7:05 pm

VMCA787 wrote:
T54A wrote:
The B727-200 with the JT8D-17 was ok. Those powered by the -15 were a bit lazy getting airborne.[/quote

Obviously, you have never flown in a 200 with-7 engines!!!


:lol: I was thinking the same thing! We were happy to get -15's!
 
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Duderocks5539
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Sep 22, 2021 7:05 pm

On an unrelated note, when the JT8D-209, 217, and 219 came out, the JT8D-1 through -17R as well as JT3D's were absolutely laughing stocks when it came to fuel efficiency and noise. On the last 727s built, Boeing put JT8D-217s on the #1 and #3 locations, but left the JT8D-1 through -17R variant engine in the #2 spot since the JT8D-200s are a much larger engine, Boeing didn't feel like modifying the tail section of the plane to fit it since the plane was already nearing the end of production.

So they just added the 12 lobe hush kit mixer in the tailpipe, and only used the engine at half power since the outboard -200 engines provided most of the thrust, and also so the noise levels from the -1 to -17R match the -200s, because if that single -1 to -17R was at full power despite having a hush kit, its sound would override the -200s which those at full power are the same noise levels as a hush kitted -1 to -17R at half power!

Later on, certain operators wanted to have the -200 engines on their 72s, so then the Super 27 conversion was launched by Valsan in the 1990s.
 
GalaxyFlyer
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Sep 22, 2021 8:17 pm

Were there new build 727 with -217 power? If so, I missed it. The last new builds were for FDX at 206,000 TOGW and i thought with -17R power.
 
744SPX
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Re: Why didn't Boeing power the 727 with JT3D engines?

Sun Sep 26, 2021 7:03 am

A 727-100 with the -17R's would have been sporty. Don't know if that combo was flown though.
 
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tb727
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Re: Why didn't Boeing power the 727 with JT3D engines?

Mon Sep 27, 2021 12:31 am

744SPX wrote:
A 727-100 with the -17R's would have been sporty. Don't know if that combo was flown though.


Nygard's now former/scrapped 721 had -217's on 1&3 and I think a -15 in #2. A real rocket I'm sure!
 
AvgWhiteGuy
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Re: Why didn't Boeing power the 727 with JT3D engines?

Mon Sep 27, 2021 2:00 am

tb727 wrote:
744SPX wrote:
A 727-100 with the -17R's would have been sporty. Don't know if that combo was flown though.


Nygard's now former/scrapped 721 had -217's on 1&3 and I think a -15 in #2. A real rocket I'm sure!


My dad flew that for Nygard up until the last flight, I can ask him...
 
744SPX
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Re: Why didn't Boeing power the 727 with JT3D engines?

Mon Sep 27, 2021 4:58 am

AvgWhiteGuy wrote:
tb727 wrote:
744SPX wrote:
A 727-100 with the -17R's would have been sporty. Don't know if that combo was flown though.


Nygard's now former/scrapped 721 had -217's on 1&3 and I think a -15 in #2. A real rocket I'm sure!


My dad flew that for Nygard up until the last flight, I can ask him...


Cool!
 
GalaxyFlyer
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Re: Why didn't Boeing power the 727 with JT3D engines?

Mon Sep 27, 2021 1:19 pm

tb727 wrote:
744SPX wrote:
A 727-100 with the -17R's would have been sporty. Don't know if that combo was flown though.


Nygard's now former/scrapped 721 had -217's on 1&3 and I think a -15 in #2. A real rocket I'm sure!


A good friend flew Getty’s Valsan conversion, yes a rocket til it runs out of wing. It was built as a corporate model, -100 fuselage with -200 wing and gear, IIRC. My question is, did Boeing build a -217 powered B727 out of the production line?
 
744SPX
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Re: Why didn't Boeing power the 727 with JT3D engines?

Mon Sep 27, 2021 6:01 pm

GalaxyFlyer wrote:
tb727 wrote:
744SPX wrote:
A 727-100 with the -17R's would have been sporty. Don't know if that combo was flown though.


Nygard's now former/scrapped 721 had -217's on 1&3 and I think a -15 in #2. A real rocket I'm sure!


A good friend flew Getty’s Valsan conversion, yes a rocket til it runs out of wing. It was built as a corporate model, -100 fuselage with -200 wing and gear, IIRC. My question is, did Boeing build a -217 powered B727 out of the production line?


I would be very surprised if they did.
 
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tb727
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Sep 29, 2021 12:45 am

GalaxyFlyer wrote:
tb727 wrote:
744SPX wrote:
A 727-100 with the -17R's would have been sporty. Don't know if that combo was flown though.


Nygard's now former/scrapped 721 had -217's on 1&3 and I think a -15 in #2. A real rocket I'm sure!


A good friend flew Getty’s Valsan conversion, yes a rocket til it runs out of wing. It was built as a corporate model, -100 fuselage with -200 wing and gear, IIRC. My question is, did Boeing build a -217 powered B727 out of the production line?


My friend was an FE on it once in a while, he did say it was a nice plane.

I don't think Boeing ever had a -217 powered one off the line. The first Valsan mod flew in 1988.
 
AvgWhiteGuy
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Re: Why didn't Boeing power the 727 with JT3D engines?

Wed Sep 29, 2021 1:59 pm

So dad knows the pods on Nygard's were 217's, and said #2 was a -7 or -9, but thought it to be the original type. He said they operated #2 normally, not
pulling it back in relation to 1 and 3.
Coincidentally, he is leaving in a few hours to fly an around-the-world trip for Geoff Palmer, who also has a 72 with 217's and an original type #2.
As I'm an ex Delta 72 engineer, this is a very cool thread!

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