Ttailsteve
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DC-8 And Reverse Thrust Use In Flight

Mon Jul 03, 2006 12:50 pm

I remeber reading an accident report in the distant past, I think possibly Eastern Airlines where the crew averted an accident and recovered the aircraft by using the in-board thrust reversers in flight. Why and When were the Dc8s allowed to use thrust reverse. Anyone recall this specific incident?
 
n8076u
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DC-8 And Reverse Thrust Use In Flight

Mon Jul 03, 2006 1:09 pm

DC-8s could always use reverse thrust in flight (except for the first one, in the beginning, I'll explain below). This was because of the fact that it does not have spoilers than can be used in flight to slow it down (it does actually have spoilers, but they are for use on the ground only). Depending on which particular model it was, power settings up to full reverse thrust could be used on all four engines in flight, or idle reverse on the outboard engines and full reverse thrust on the inboards.

The first DC-8 that flew at the beginning of the flight test program did not have any thrust reversers at all at the time. It did have "fighter" style speedbrakes in the back of the fuselage. They were found to be completely ineffective, and so were not installed on any further production aircraft. Thrust reversers were later installed on this first aircraft, along with other various upgrades, and consequently, on all further DC-8s.

Chris
Don't blame me, I don't work here...
 
ANother
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 2:10 am

I remember this, landing in ATH in the late 70s. CP Air DC8-43 (can't remember which Empress). The captain warned us that he was about to do this - apparently he was given a direct approach and needed to lose altitude fast. We did!

[Edited 2006-07-03 19:10:57]
 
JJMNGR
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 2:13 am

And as far as I know it is possible to apply reverse just on engines number 02 and 03. Am I correct?
 
n8076u
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 2:54 am

Quoting JJMNGR (Reply 3):
And as far as I know it is possible to apply reverse just on engines number 02 and 03. Am I correct?

Yes, you can use just #2 and #3 if you want to. According to pilots that I've talked to, using just #2 and #3 reversers in flight is what they usually do if they do it at all. Apparently, it is a somewhat harsh event to experience...

Chris
Don't blame me, I don't work here...
 
BrowntailWhale
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 3:55 am

The way it works is this, with the gear up, only #2 and #3 can be reversed. They can go up to max thrust. With the gear down all four can be reversed up to max thrust
 
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rg828
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 8:14 am

Those DC-8 pylons must have been made from cast iron to withstand those forces.

Amazing stuff.
I dont know the key to success, but the key to failure is trying to please everyone
 
irobertson
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 9:05 am

Quoting RG828 (Reply 6):

Might be one of the reasons so many are still going... a real amazing plane... If airline manufacturers could really master this fuel efficiency thing, they should really consider making planes that are similarly strong with potential lifespans that match it or better. If Douglas could do it in the 1950s and 60s, we should be able to do it now.
 
ImperialEagle
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 10:34 am

I experienced many a flight on DL's DC-8-50's when the reversers were deployed in flight. I used to try to get the window seat by the seat next to #2 or #3, just so I could watch the action! It really got your attention, and it was VERY effective!

Those old Pratts really danced around in the nacelles----I can hear them now------------awesome!
"If everything seems under control, you're just not going fast enough!"
 
MontanaFL
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 12:36 pm

This isnt about the DC-8 which I loved to fly on but on the site "Flight Level 350" is a video of a C-17 using the two inboard engines in reverse to do a "tactical decent" from 20, 000 to 11, 000 - 13, 000 fpm. The author stated that the shaking was from the reverse thrust in flight. Hope the link below works. Rather interesting.

http://www.flightlevel350.com/Aircra..._Untitled_Aviation_Video-5025.html
I miss those DL L-1011's
 
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rg828
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 1:34 pm

Quoting ImperialEagle (Reply 8):

Those old Pratts really danced around in the nacelles----I can hear them now------------awesome!

I bet they did!
Despite the fact this inflight-reversing is a well-known DC-8 trait, I have never seen an action shot of it.
I dont know the key to success, but the key to failure is trying to please everyone
 
n8076u
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RE: DC-8 And Reverse Thrust Use In Flight

Tue Jul 04, 2006 4:37 pm

Quoting BrowntailWhale (Reply 5):
The way it works is this, with the gear up, only #2 and #3 can be reversed. They can go up to max thrust. With the gear down all four can be reversed up to max thrust

Actually, what you wrote does not apply to all DC-8s, and is not true regarding any of the 60-series and older DC-8s that UA had. Perhaps what you said applies to the 70 series with the CFMs? Here's a breakdown of the models I have information on:

THRUST BRAKE LIMITATIONS--IN FLIGHT

--The -10 series, with JT3C engines could go to max continuous power on all four, regardless of the gear position.

--The -20 and -30, with JT4A engines could go to max continuous power on #2 and #3, and had mechanical stops which limited #1 and #4 to approx. 31% of max continuous power (gear up or down) until there was weight on wheels, at which point #1 and #4 could go to max continuous.

--The -40 I have no information about. Sorry RR fans...

--Most -54F, and all -61, with JT3D turbofans could use #2 and #3 up to max continuous. On #1 and #4, no reverse with gear up, limited to idle reverse by mechanical stops with gear extended. With weight on wheels, #1 and #4 could to go max continuous.

--All the other -50 series not covered above, and all -62 with JT3Ds could use #2 and #3 up to max continuous, #1 and #4 were locked out of reverse, even with gear down, until there was weight on wheels.

--I have no info for the -63 or any of the -71/72/73.

--Max speed for extending ejectors and/or using thrust brakes: 390kts.
--Max speed for retracting ejectors (JT4A): 250kts.
--Thrust reversers must not be used in flight below a speed of 200kts.
--Wing flaps must be completely retracted for all inflight thrust brake applications.

FYI, all this information was taken from a UA DC-8 flight manual.

Chris
Don't blame me, I don't work here...
 
cf6ppe
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RE: DC-8 And Reverse Thrust Use In Flight

Thu Jul 06, 2006 11:51 am

Great job Chris, listing the DC-8 THRUST BRAKE LIMITATIONS--IN FLIGHT.

It has been more than thirty years since I had the pleasure of working on the DC-8's.

One of the things that I remember was that the squat switch for reverser operation on the ground was on the nose gear. There were many pilot write-ups for not being able to get reverse thrust due to landing on the main gear and keeping the nose up in a draggy configuration, but not as effective as having the reversers at maximum allowable power during the landing roll out.

The series -63 had the same reverser configuration as the -62 series. I presume that the -63 had the same limitations as the -62's.

One of the main in-flight uses of the DC-8 reversers was to be able to keep the engine power slightly above idle - approx. 1.05 or 1.06 EPR - so that the generators would stay on line in descent. If one kept the power in forward thrust at those power settings (to keep the generators on line) the aircraft descent speeds were higher and the descent took longer.

The DC-8 fleet that I powerplant engineered over consisted of fourteen ea. -21 series, three ea. -51 series, seventeen ea. -61 series and six ea. -63 series.
 
xaphan
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RE: DC-8 And Reverse Thrust Use In Flight

Thu Jul 06, 2006 1:28 pm

I was non-reving on a DL DC 8 61 inbound to ATL on descent when #2 and 3 went into reverse. Looking out the window (I was seated toward the back of first class) I saw a Southern Martin 404 breaking through the cloud cover directly below us, close enough to be considered a "near miss". I said a silent prayer of thanks to the Douglas engineers who designed that feature.

Another exciting feature of the engines was the starting. They had a real Banshee's scream, especially on a cold O'Hare night!
 
connies4ever
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RE: DC-8 And Reverse Thrust Use In Flight

Thu Jul 06, 2006 7:27 pm

Not sure about the thrust setting limit, but several times on AC DC-8-40s I experienced in-flight use of the thrust reversers. Captain would always come on and advise people that there will be some noise and bumpy flight for a couple of minutes -- and there was! Like being on an elevator.
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