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What Is Louder JT3 Or JT8?  
User currently offline747400sp From United States of America, joined Aug 2003, 3301 posts, RR: 2
Posted (7 years 10 months 1 day 22 hours ago) and read 2484 times:

I wanted to know with out hush kits, which is louder JT3 or JT8? Growing up I herd a lot of 727 and MD80 but even though they were loud I thought 707 was the loudest plane next to a C-5 I ever herd, until I herd a F-18, F-16 F-15 and F-22. But reading some of these post, it has been stated that older JT8 powered aircraft or very loud. I also remember a Canadian 737 200 coming in to LAX flew near my house that was pretty loud. A lot of DC-8 super 60 that I herd was not that loud and the C-141's that use to come into LAX was not to loud ether. I believe JT3 win this contest because of the 707 including Air Force two or V-137 and an Evergreen International DC-8-62 I have herd, but I wanted another opinion.

13 replies: All unread, jump to last
 
User currently offlineSovietjet From Bulgaria, joined Mar 2003, 2519 posts, RR: 17
Reply 1, posted (7 years 10 months 1 day 20 hours ago) and read 2471 times:
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From what I've heard they are pretty equal however I would have to give it to the JT-3. It's a bit louder, but it also has that "screech". I assume you're talking about JT-3Ds and not JT-3Cs because the C's would definetly win by far as they are pure turbojets.

User currently offlineN8076U From United States of America, joined Jun 2006, 425 posts, RR: 9
Reply 2, posted (7 years 10 months 1 day 16 hours ago) and read 2454 times:

You need to be more specific, as just saying "JT3" could mean the JT3C turbojet or the JT3D turbofan. And the "JT8" is the JT8D turbofan.

Regardless, the turbojet was the loudest, hands down, by far. Then the turbofan JT3D and JT8D, which were both pretty damn loud by today's standards, but I think I would pick the JT3D as the louder of the two. That is without any more modern hushkits for the turbofans. No hushkit in the world could help the turbojet.  Wink

The thing about the DC-8 super 62 and 63 is they had a new nacelle design that made a lot of difference in decreasing the noise footprint, even with the increased thrust of the newer engine version, the JT3D-3B. The ones with hushkits are actually a disappointment when watching them takeoff, as you keep waiting to hear the engine go to takeoff power, when you realize it already is, and away it goes...quietly.  Wink


Chris



Don't blame me, I don't work here...
User currently offlineDc863 From Denmark, joined Jun 1999, 1558 posts, RR: 2
Reply 3, posted (7 years 10 months 1 day 6 hours ago) and read 2413 times:

JT3 by far is much louder than any JT8. As for the DC-8-62/63s their nacelle design did little to minimize the noise.

User currently offlineN8076U From United States of America, joined Jun 2006, 425 posts, RR: 9
Reply 4, posted (7 years 10 months 1 day 3 hours ago) and read 2395 times:

Quoting Dc863 (Reply 3):
JT3 by far is much louder than any JT8. As for the DC-8-62/63s their nacelle design did little to minimize the noise.

I know the JT3D was louder than the JT8D, but I only had my opinion to base that on and didn't want to say more than it was in fact louder, as I have had little exposure to the JT3D compared the JT8D.

I have read in a book that LaGuardia was thinking of banning the "super 60's" from using its facility due to excessive noise concerns, especially the 62/63, but this was before the 60 series was actually introduced into service. This was going to possibly affect orders from one of the airlines that used LaGuardia, and so Douglas performed noise tests there, and proved that the 61 was no louder than the 50 series, and that the 62/63 were actually quieter than the 61's even with the higher thrust engines, so that is what I based my statement on regarding the nacelles.

Chris



Don't blame me, I don't work here...
User currently offlineIrish251 From Ireland, joined Nov 2004, 959 posts, RR: 4
Reply 5, posted (7 years 10 months 14 hours ago) and read 2362 times:

Quoting N8076U (Reply 4):
I have read in a book that LaGuardia was thinking of banning the "super 60's" from using its facility due to excessive noise concerns, especially the 62/63, but this was before the 60 series was actually introduced into service. This was going to possibly affect orders from one of the airlines that used LaGuardia, and so Douglas performed noise tests there, and proved that the 61 was no louder than the 50 series, and that the 62/63 were actually quieter than the 61's even with the higher thrust engines, so that is what I based my statement on regarding the nacelles.

There are no LGA DC-8 (or 707) photos in the site's database and this supports my belief that these types did not serve La Guardia - using JFK or EWR instead.


User currently offline113312 From United States of America, joined Apr 2005, 564 posts, RR: 1
Reply 6, posted (7 years 10 months 13 hours ago) and read 2355 times:

The JT-3 series was louder than the JT-8. However, "louder" is both a quantitative and qualitative term. You can get db values for each engine in their original installations to make the quantitative comparrisons. It should be noted, the original JT-3, JT-3C and even JT-4 turbojets had "organ pipe" sound suppressors on Boeing jets and a similar array plus the ejector ring in the DC-8-10/20/30 installations. Military J-57 and J-75 versions of these engines didn't have any sound suppression and were even louder.

The introduction of the JT-3D series Turbofan for the Boeing 707/720B and DC-8-50/60 series provided the first reduction in maximum noise. As a listener, the difference would only be apparent by side by side comparrison as they were still pretty loud.

The JT-8D engine was developed for the B727 and DC9 as a neighbor friendly turbofan powerplant that was noticably quieter than all of the JT-3/4, CJ-805, and Rolls Royce Conway powerplants in use on the 4 engine airliners. However, as the JT-8D progressed with higher and higher thrust outputs, again the maximum noise increased. This is why many DC9s seemed so loud when powered with the JT-8D-17.

The requirements for reduced noise introduced Stage II, and later Stage III standards. Inlet treatments and exhaust modifications reduced the noise values of all of the engines. Unmodified planes were banned from many locations. Because many younger observers have only experienced DC-8s and B707s in recent years that were modified to Stage II or III standards, it is understandable why they might not perceive the noise differences with the JT-8 powered planes in compliance with the same standards.

All jets operating today must meet Stage III nearly everywhere. But a new Stage IV standard is emerging and the cycle of noise reduction and obsolescence starts again.

But, returning to the historic context, remember that Eastern Air Lines was the launch operator of the Boeing 727 with the then new and revolutionary JT-8D-1 powerplant. They dubbed these planes "WhisperJet" to market their new good neighbor quality.


User currently offlineDc863 From Denmark, joined Jun 1999, 1558 posts, RR: 2
Reply 7, posted (7 years 10 months 13 hours ago) and read 2348 times:

No DC-8 ever served LGA. I'm sure this had something to do with the runway length during the 1960s.

User currently offlineN8076U From United States of America, joined Jun 2006, 425 posts, RR: 9
Reply 8, posted (7 years 10 months 11 hours ago) and read 2332 times:

I must have named the wrong airport this occured at, but I will look it up when I get home and post what I find.

Chris



Don't blame me, I don't work here...
User currently offlineN8076U From United States of America, joined Jun 2006, 425 posts, RR: 9
Reply 9, posted (7 years 9 months 4 weeks 1 day 16 hours ago) and read 2265 times:

According to Terry Waddington in his book Great Airliners Volume2: DC8, the Port Authority of New York was concerned about noise and threatened to ban the DC-8-61 from JFK (sorry about mentioning LGA, don't know where that came from) due to takeoff noise. Eastern was concerned, as they had quite a few 61's on order. A demonstration was held, and it was found that exhaust noise from the -61 was "slightly less" than a -55JT.

He goes on to say that the new long duct pod on the 62/63 improved fuel efficiency by 8.5% over the 50 series, improved takeoff performance, and reduced the takeoff noise by 2.5 decibels and approach noise by 4.5 decibels over the 50 series levels.

Chris



Don't blame me, I don't work here...
User currently offlineTimz From United States of America, joined Sep 1999, 6708 posts, RR: 7
Reply 10, posted (7 years 9 months 4 weeks 1 day 16 hours ago) and read 2261 times:

Quoting Dc863 (Reply 7):
No DC-8 ever served LGA. I'm sure this had something to do with the runway length during the 1960s.

AFAIK no 4-jet airliner was ever scheduled into LGA. But Northeastern did fly DC-8s off of ISP's 6000-ft (at the time) runway.


User currently offlineDc863 From Denmark, joined Jun 1999, 1558 posts, RR: 2
Reply 11, posted (7 years 9 months 4 weeks 1 day 11 hours ago) and read 2232 times:

Quoting Timz (Reply 10):
But Northeastern did fly DC-8s off of ISP's 6000-ft (at the time) runway.

That must've been a sight to behold. The flight crew must've stood on the brakes while applying takeoff thrust. I'm sure that woke up the neighbors.


User currently offlineImperialEagle From United States of America, joined Jan 2006, 2065 posts, RR: 20
Reply 12, posted (7 years 9 months 2 weeks 5 days 22 hours ago) and read 2111 times:
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JT-3's without thrust reversers and "daisy-petals" such as the military KC-135's. Without a doubt the loudest engines (at take-off power) I ever experienced on a transport aircraft---bar none!


"If everything seems under control, you're just not going fast enough!"
User currently offlineLongHauler From Canada, joined Mar 2004, 4760 posts, RR: 43
Reply 13, posted (7 years 9 months 2 weeks 5 days 19 hours ago) and read 2104 times:

Quoting Dc863 (Reply 7):
No DC-8 ever served LGA.

Air Canada flew the DC-8-53 into LGA in 1979/1980. It was the last flight of the day YYZ-LGA, and the first flight out LGA-YYZ.



Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
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