Why planes are slower?

Something the article didn't mention is fuel savings and gate space. I was at a Delta Regional and Delta has a program where you were required to fly at a certain speed, often down in the low .70 mach numbers. Gate space was/is an issue at ATL for instance, and they didn't want you arriving real early and have to wait 10-15 minutes or more for a gate. Of course this was ignored on the "going home, last leg" flight. :D
 
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Braniff used to fly at .90 at least, then during the fuel crunch they started doing reduced power takeoffs. First one I experienced I was concerned, didn't know they were doing it on purpose. All about fuel. People's Express locked out the 40 flaps setting to save fuel on the 727. We put a micarta block on the gate to lock it out.
 
Yep we did reduced thrust take offs also.
 
So, this guy makes a totally bs YouTube movie and it gets picked up by popular mechanics?

And no one bothered to talk to anyone about aviation?

I get the local news reporter flubbing their way thru in an effort to get things reported quickly, but this is just dumb.
 
Paulie said:
during the fuel crunch they started doing reduced power takeoffs.
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Reduced-thrust takeoffs actually burn a little more fuel than full-power takeoffs because it takes longer to reach the point where power is reduced to climb-power. The benefit is in increased engine life.
 
I didn't realize that it <according to the article> is dangerous to fly at near the speed of sound. I guess those pilots of supersonic military types cheat death twice on each Mach 1 plus flight.
 
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Can someone sum up in twenty words or less what the issue is?
 
Larry in TN said:
Reduced-thrust takeoffs actually burn a little more fuel than full-power takeoffs because it takes longer to reach the point where power is reduced to climb-power. The benefit is in increased engine life.
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I very much doubt that the airline (Braniff) was doing it for engine life while they were buying fuel on the spot market and prices were soaring.
 
kyleb said:
I didn't realize that it <according to the article> is dangerous to fly at near the speed of sound. I guess those pilots of supersonic military types cheat death twice on each Mach 1 plus flight.
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Killed several P-38 pilots. They did not realize it was flying into the transonic speed range that was causing severe buffeting and killing pilots. If you notice on the elevators for P-38’s they added top and bottom counter weights in an attempt to cure buffeting at high speeds.
 
Briar Rabbit said:
Killed several P-38 pilots. They did not realize it was flying into the transonic speed range that was causing severe buffeting and killing pilots. If you notice on the elevators for P-38’s they added top and bottom counter weights in an attempt to cure buffeting at high speeds.
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The P-38 had a mass balanced elevator with external counterweights from day 1. Google images of P-38 prototype and you'll see them.

The article made a blanket statement that it is dangerous flying near the speed of sound, which is not correct. It is plenty safe to fly in that regime if the airplane is designed for it.
 
Briar Rabbit said:
Killed several P-38 pilots. They did not realize it was flying into the transonic speed range that was causing severe buffeting and killing pilots. If you notice on the elevators for P-38’s they added top and bottom counter weights in an attempt to cure buffeting at high speeds.
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I believe on the P-38 the changes were a small flap like surface mid-chord on the bottom of the wing and the large wing root fairing to deal with transonic flow.
 
I think you guys are being a little hard on the video. Yes, it oversimplifies some things. But the target audience is not highly experienced pilots, mechanics, and engineers like we have on this site. As a lowly experienced, non-military, non-commercial pilot, I found it interesting.
 
kyleb said:
The P-38 had a mass balanced elevator with external counterweights from day 1. Google images of P-38 prototype and you'll see them.
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Please refer to this article, second paragraph below is a cut & paste:
https://en.wikipedia.org/wiki/Lockheed_P-38_Lightning
Other info from various printed sources.

Lockheed’s P-38 was the first fighter to fly faster than 400 mph. It was already in production in the fall of 1941 when some alarming problems started showing up in test flights: in high speed dives the plane would shake violently, the controls would seem to lock up, and the nose would tuck under, sending the plane into an ever-steeper dive. On November 4, 1941, test pilot Ralph Virden was killed when he could not pull out of one of these dives.

In 1941 flutter was a familiar engineering problem related to a too-flexible tail, but the P-38's empennage was completely skinned in aluminum[Note 2] rather than fabric and was quite rigid. At no time did the P-38 suffer from true flutter.[38] To prove a point, one elevator and its vertical stabilizers were skinned with metal 63% thicker than standard, but the increase in rigidity made no difference in vibration. Army Lieutenant Colonel Kenneth B. Wolfe (head of Army Production Engineering) asked Lockheed to try external mass balances above and below the elevator, though the P-38 already had large mass balances elegantly placed within each vertical stabilizer. Various configurations of external mass balances were equipped, and dangerously steep test flights were flown to document their performance. Explaining to Wolfe in Report No. 2414, Kelly Johnson wrote "the violence of the vibration was unchanged and the diving tendency was naturally the same for all conditions."[39] The external mass balances did not help at all. Nonetheless, at Wolfe's insistence, the additional external balances were a feature of every P-38 built from then on.[40]

All the experts consulted were baffled until John Stack diagnosed the problem: the compressibility burble was causing the wing to lose lift; that altered the angle of the air leaving its trailing edge and striking the tail, in turn generating increased lift on the tail which pitched the tail up—and the nose down.

The '38 was first plane to suffer from compressability because it was the first one to achieve the speed required to hit compressability. The "dive recovery flaps" installed on the 'J-25 and L models didn't fix compressability, but made it possible to manage it. The F4U and P-47 also ran into compressability issues, with at least the '47 also being equipped with dive recovery flaps.

This situation was aggravated by the early problem of the nacelle slipstream going supersonic and essentially locking the rear elevators. Deadly in a dive when exceeding a certain speed. Took them several planes to figure out what was going on. A small flap was added to break up the stream. "Fix-kit"s were sent out to retro fit early models. The aircraft carrying them to Europe was shot down and they did not arrive. The P-38's were not allowed to follow the enemy planes in a high speed dive until the production airplanes were equipped with the dive recovery flaps.

The elevator balance weights were originally internal but had to have mounted external counter balance weights to satisfy misconceptions of the Air Force brass.
Yep. External ones were redundant, it retained the internal ones.
 
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Paulie said:
I very much doubt that the airline (Braniff) was doing it for engine life while they were buying fuel on the spot market and prices were soaring.
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Reduced-thrust takeoffs do not save fuel. They burn a bit more fuel. They do significantly extend the life of the engine's hot-section which is their primary benefit.
 
Larry in TN said:
Reduced-thrust takeoffs do not save fuel. They burn a bit more fuel. They do significantly extend the life of the engine's hot-section which is their primary benefit.
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You can keep saying that but like I said the only time the were used is when they were buying on the spot market. Repeating it again will not change history.
 
Paulie said:
You can keep saying that but like I said the only time the were used is when they were buying on the spot market. Repeating it again will not change history.
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I don't know what or why Braniff did what it did but the procedures of a failed airline don't change physics.

With reduced-thrust takeoffs you stay in takeoff power longer as the power reduction to climb-power is based on altitude-gained. Longer time spent at the higher takeoff thrust results in a greater fuel burn for the takeoff. The savings from reduced-thrust takeoffs comes from the extended life of the engine's hot-section due to the significantly lower internal temperatures at the reduced-thrust power settings.
 
Larry in TN said:
I don't know what or why Braniff did what it did but the procedures of a failed airline don't change physics.

With reduced-thrust takeoffs you stay in takeoff power longer as the power reduction to climb-power is based on altitude-gained. Longer time spent at the higher takeoff thrust results in a greater fuel burn for the takeoff. The savings from reduced-thrust takeoffs comes from the extended life of the engine's hot-section due to the significantly lower internal temperatures at the reduced-thrust power settings.
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Agree. You can buy one helluva lot of JetA for the cost of a hotsection overhaul.

Cheers
 
Paulie said:
OK I believe you. Happy now?
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Here's what Boeing has to say about it.

From a fuel consumption perspective, a full-thrust takeoff and a full-thrust climb profile offer the most fuel economy for an unrestricted climb. However, from an airline’s cost perspective, this must be balanced with engine degradation and time between overhauls, as well as guidance from the engine manufacturer. The airline’s engineering department must perform the analysis and provide direction to flight crews to minimize overall cost of operation when using takeoff derates or assumed temperature takeoffs and climbs.
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http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_08/article_05_3.html
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kyleb said:
Airlines choose to fly slower to save fuel both enroute and to avoid arriving prior to their landing slot(s).
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This leads to some funnies, as I heard. One: a couple of years ago a stick shaker activated on a CRJ for one of regionals in the U.S. Two: An-148 has an ability to tool along at 0.7 Mach, which causes consternation among pilots and controllers alike (or so I heard -- I don't know why Munich or Warsaw cannot just tell him "keep the speed Mach 0.82 or above").
 
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