Why Do Planes Climb So Steeply at Takeoff?

Ron Wagner:

I’m going to guess that you mean commercial airliners on which you ride “go so steep.” Obviously, you feel they go steep, but “steep” is a relative term—one person’s “steep” is another person’s “boring.”

I’LL SHOW YOU “STEEP”

I had the good fortune to get taxpayer-funded pilot training through the U. S. Air Force, which included flying the Northrop T-38 Talon supersonic jet. When it was first introduced, it was the fastest-climbing aircraft in the world and set the world time-to-climb record.

The specific jet they used to set that record had the tail number of 10849. After that record-setting flight, 849 went to the regular training fleet at Webb AFB in Big Spring, Texas, which is where I went to pilot training. The folks at Edwards AFB, where the record was set, painted a list of the various records it had set on the nose, but otherwise, that jet was just a regular member of our fleet at Webb.

Eleven years later, I got to fly 849. Unfortunately, back then there was no such thing as smartphone cameras. If I’d had one, I would have gotten someone to take a pic of that list of records on the nose with me sitting in the cockpit—but, alas!

The records were set in meters, and they ticked off a bunch of them, but the easy one to remember is the climb to 9000 meters because that’s 30,000 feet.

The climb record must be measured from the moment the aircraft first moves on the runway, all the way through takeoff, gear up, and then start climbing. That whole process—from dead-stop on the runway to 30,00 feet—took 62 seconds ... and here’s a photo taken that day, like a scalded angel trying to get back to heaven.

Now that’s what I call a “steep” takeoff.

Airliners do not take off “steep.”

BUT AIRLINERS DON’T HANG AROUND AT LOW ALTITUDE

Jet aircraft are most efficient at high altitudes. The most fuel efficient profile any jet can fly on a cross-country trip would be to climb at its maximum rate all the way to cruising altitude, level off and pull back to cruise power, and stay there until the precise moment the engines can be pulled to idle and descend to a landing.

Due to traffic and passenger comfort, the airliners don’t fly that maximum efficiency profile, but they try to get close.

And that’s why it seems to you that jet airliners climb “relatively steep,” but trust me, they do not fly steep. That T-38 climbed steep!

JUST FOR THE RECORD

A few years later, the F-4 broke the T-38′s record. I haven’t followed the latest, but I clearly recall in 1975 when the F-15 brought the 9000 meter record down to 48.8 seconds.

I just watched a video of an airliner takeoff and saw that it broke ground at about 50 seconds after brake release and they raised the gear at about one minute after brake release.

And so, to simplify this: From brake release, the F-15 can be at 30,000 in the time that a typical airliner is just raising its nose on the runway. Forty. Eight. Point. Eight. Seconds.

The F-15 has a thrust-to-weight ratio of greater than one, which means it can accelerate going perfectly vertical, like a ballistic rocket.

Now that, my friends, is the ultimate in “steep.”

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