# DB Coopers escape

I am fairly sure that the hijacker departed the in flight 727 via the drop down boarding ladder at the rear of the plane…after donning a parachute, of course.

I see!

Let’s assume that heyitsbob is referring to the classic column reprinted this week entitled Can you open an airliner emergency door while the plane is in mid-air?

My understanding is that the 727’s boarding ladder did not have a plug design, and thus could be opened in fight relatively easily.

After DB Cooper’s adventure, Boeing retrofitted 727s with a “Cooper vane” that prevented the door from opening while the plane was in motion. (Basically, it’s an external locking lever activated by air passing over the fuselage.)

Said column includes a significant error:

The second sentence is accurate; the first isn’t: 7psi corresponds to an altitude of around 19,000’. Passengers in a cabin at that pressure would soon be hypoxic (actually not - oxygen masks would have deployed when cabin altitude was around 10,000’).

Airliners typically operate with cabins at pressure altitudes between 5000 and 7000 ft, corresponding to pressures between 12.2 and 11.3 psi.

FWIW, the cabin pressure and humidity settings for the 787 will allow for higher settings as a result of the composite structure.

Higher in the sense of higher pressure, rather than higher altitude. Various Googling suggests the cabin altitude will be around 6000 ft.

To be more precise, yeah. Cabin pressure is going to be a function of the aircraft’s altitude. The 787 is rated for a service ceiling of 43,000 feet. So your maximum pressure differential will be 11.3 - 2.3 = 9.0 psi.

This is presuming the cabin pressure is going to vary with respect to the altitude the plane is flying. If the altitude is say 30,000 feet they’ll allow a slightly higher cabin pressure (or “lower altitude”)as opposed to a lower cabin pressure (“higher altitude”) of 39,000 feet.

YAMV.