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33

(airliners.net) Ejector on the Rolls-Royce Conway of a DC-8. It's called an ejector. Introduced in c. 1958 by Douglas for their DC-8, it is extended during takeoff and landing, and stowed during the flight because it increases the drag at high-speed flight. In the extended position it acts as a noise suppressor, and it also reclaims thrust that has been lost ...


7

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, disrupting everything behind it, and which would include a significant component of flow over the top of the wing. The tufts show some straight and some pointing ...


6

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 60 series aircraft already in use. So it’s really not correct to say “a CFM56-powered version of the DC-8 became available in 1982.” More like a CFM56 retrofit ...


6

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, but this margin is mandated by the certification authority so you can't use it. The design won't have much more than the required margin because that would make ...


6

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 and creates drag at higher speeds, and then it is extended during the descent/approach phase. It is operated hydraulically to extend and retract, and can be ...


5

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 costs through improved revenue or decreased operating expenses. Looking at your references, there was some structural changes to the wing and landing gear ...


5

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 to release pressurized air into the hydraulic brake system in the event of hydraulic pressure loss, as explained in this AAIB bulletin. The fuselage air brakes ...


3

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 (-135s in general), and other variants like the E-3, E-6, E-8, C-18, and C-137. Because the US military had such a large fleet of the 707 family, they acquired as ...


3

What you're missing from your diagram is @JohnK's drawing (which I'll borrow) from his answer to your related question, Why does the use of reverse thrust in flight on the DC-8 cause areas of separated/reversed airflow over the wing? The use of reverse thrust increases the wing's angle of attack (AOA) more than it does for the tailplane (as opposed to if ...


2

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 fitted to accommodate the hush kit nozzle.


2

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 emergency decent all throttles are retarded to idle and the inboard thrust brake levers are put into "Reverse Detent Thrust" and when the "Eng Thrust Brake" ...


1

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 closer to the wing root, which is safer than doing so on the outboard engines. Farther outboard the force of the buffeting might damage the wing's mechanisms or ...


1

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 noise attenuation benefits it was not part of a hush kit. The Conway engine was very responsive but also very noisy. Later DC-8, fitted with Pratt & Whitney ...


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