How about a little quiz on the Boeing planes?

Why do the 727 and 737 have different leading devices inboard and outboard?

What about the 707 and the 747???

Lou

The 727 has a clean wing, therfore no nacelles in the way, and the 737 does have nacelles in the way.

The 747 has two settings of leading edge flaps rather than one.

Does it have to do with critical airfoil?

J/K is just about to hit the target. Peter, don't let him beat you!  

Think about where you want the wing to stall last.

Hint: washout  

J/K,

Here is a side view drawing of a Kruger leading edge flap on the 727, 737.



And here is a photo of the same flap on a R W 737...



Here is the L E flap on the 747...



These are all forms of Kruger L E flaps.

My question is:

First, why the mix of Kruger and slats on the 727 & 737?

Second, why does the 707 and 747 have only Kruger L E flaps?

J/K, if you would like to answer, be my guest.  

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Correct!

There are two questions to answer here...

First, why the mix of Kruger and slats on the 727 & 737?

The Kruger flap is a pretty basic device. It folds forward from below the leading edge & diverts airflow over the top surface of the wing. More airflow flow over the top of the wing equals more lift. Air is trapped behind the flap and acts as a smoothing area keeping the airflow laminar both over and under the wing. At higher angles of attack the flow breaks down where the Kruger is installed stalling that part of the wing first. These type of Kruger flaps are installed inboard on the 727 and 737 with slats outboard to insure that the wing keeps its lift on the outboard part of the wing in much the same way the wing is washed out. You want the tip to stall last so you keep roll control right to the end.

Second, why does the 707 and 747 have only Kruger L E flaps?

In the case of the 707, the early ones had no L E devices. That did not last long as they were runway hogs.





As the 707 progressed, Kruger flaps were added to the wing. The progression of the -B -BA and -BAH saw additional Kruger flaps added. The reason for the Kruger vs the slat on the early Boeing planes was probably in part a cost factor. The Kruger was cheaper to make than the slat. When the 747 came along the designers were very innovative with a mix of Kruger flat flaps on the inboard part of the wing and variable camber Kruger flaps toward the outboard part of the wing. This insured the wing would keep flying at the tip during a stall.

The Kruger flap has the job of increasing lift and then stalling the wing root early to counter the pich up at stall inherent in swept wings. The cambered leading edge of the 747 does the same thing at moderate angles of attack, but hangs in there a bit longer, giving smooth flow and lift to much higher angles. Later models of the 767 and 757 lost the Kruger and went to more of a full span slat.

Lou

J/K, this is a question I talked about a long time back in this story thread. TWA did a lot of things different back in the 60's and even into the 70's. Some of the differences were good some were stupid and cost a lot of money.

Every panel in a TWA 707, 727 was turned upside down. The reason was you turned a switch up for on. On the overhead panel Boeing considered the panel a horizontal panel, thus forward was on. TWA thought of the panel as vertical, and up was on. This philosophy was carried into later planes until Boeing said no. The guy responsible for these designs in TWA retired and thus the 767, 757 escaped the changes.  

Putting the RED emergency air brake handle on the left side of the MIP was supposed to give the pilot the ability to use the brake handle with his left hand while allowing the right hand to be able to control the reverse levers. I suppose it could be argued that the tiller would have been something the pilot would may have needed to use as well, but I think at high speed the reverse levers could have been more important.