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14 votes
Accepted

Why was the DC-8-70 successful, but not the 707-700?

I think there is a bit of a misconception in your question. The DC-8 was already out of production by the time the CFM56 was developed, so all of the DC-8 70 series are actually just retrofits of the ...
TomMcW's user avatar
  • 28.6k
9 votes
Accepted

Why does the use of reverse thrust in flight on the DC-8 cause areas of separated/reversed airflow over the wing?

That's not surprising at all. What the pictures of the tufts show, and exactly what I would expect to see, is a massive injection of turbulent reverser air into the upwash just ahead of the LE, ...
John K's user avatar
  • 132k
6 votes

What makes it safe for the DC-8 to use reverse thrust in flight?

Juan is correct, inflight reversing was a bit noisy; however, it was a MEL requirement to have the inboard reversers operational to operate above FL350. The procedure was as follows: For a steep or ...
Loren's user avatar
  • 735
6 votes
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Why does the DC-8-70 have the same MTOW as the DC-8-60, despite its more powerful engines?

But maximum takeoff weight is determined by engine power not by engine power alone. The airframe also has to be strong enough for the intended takeoff weight. There is a structural strength margin, ...
Hobbes's user avatar
  • 10.2k
6 votes
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When, exactly, were the DC-8’s airbrakes removed?

The DC-8 is equipped with emergency air brake system. This isn't the type of air brakes you might expect on an airplane, but rather on a truck. The captain could pull a handle on the instrument panel ...
fooot's user avatar
  • 73.4k
6 votes

What is this ring-shaped device behind this DC-8's jet engine?

It's an ejector and was fitted on the DC-8's equipped with JT3C, JT4A or RR Conway engines. Normally extended for T/O and landing, it is retracted in flight after T/O because it is no longer needed ...
Jeff Jarvis's user avatar
5 votes
Accepted

Why was a CFM56 conversion never offered for the short-body DC-8s?

I suspect it's because the business case just wasn't there. Every retrofit project I've been involved in boiled down to the money. Retrofits aren't cheap and ultimately the mods have to recoup those ...
Gerry's user avatar
  • 19.9k
3 votes

Why was the DC-8-70 successful, but not the 707-700?

When in the test program, the reason given was the DC-8, series 60, had a longer life span than the commercial 707 aircraft existing. The KC-135 had a lot less time on them. Worked on the program ...
user67480's user avatar
3 votes

Why was the DC-8-70 successful, but not the 707-700?

It isn't an issue with the engines, but rather a question of why the DC-8 was more popular and common in commercial service, long after the 707. You identified the key in your question: the KC-135 (-...
user71659's user avatar
  • 6,614
2 votes

What is this ring-shaped device behind this DC-8's jet engine?

People got this one partly right; it's Xenu's ride - a DC-8 (not a 707) fitted with aftermarket hush kits to reduce noise. They included a non-flush clamshell thrust reversers for the hot section ...
Romeo_4808N's user avatar
  • 73.8k
2 votes
Accepted

What makes it safe for the DC-8 to use reverse thrust in flight?

It is still considered somewhat dangerous to deploy the thrust reversers on a DC-8, but because the pilot can only do so on the inboard engines, any extreme vibration or buffeting is transmitted ...
Juan Jimenez's user avatar
1 vote

What is this ring-shaped device behind this DC-8's jet engine?

The early DC-8 fitted with Rolls-Royce Conway engines had that airframe mounted ejector type thrust reverser system, it was simple, fairly light and reliable. Even though the ejector brought some ...
rich's user avatar
  • 11

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