Jetrader - Autumn 2016 - 59

Republic XF-12 Rainbow, military reconnaissance aircraft.
Photo: Tom Wigley collection.

A Pan Am double-decker Boeing Stratocruiser over San Francisco.
A rectangular porthole for the lower deck lounge is just visible behind
the wing. Photo: University of Washington Libraries Digital Collection.

The gargantuan Convair XC-99, double-deck military freighter. Pan Am ordered the
CV-37 civilian passenger version. Photo: San Diego Air & Space Museum.

A grainy concept image of the proposed stretched 707-820,
shown here in BOAC livery. Photo: blog.AviacaoComercial.

the B-29 bomber and capable of carrying up
to 100 passengers but usually configured
for about 50 in first-class comfort. Pan Am
advertised it as a double-decker because
there was a tiny lounge in the lower hold,
reached by a spiral staircase from the main
deck. Of the total 1949-1950 production
run of 55 Stratocruisers, Pan Am had 29.
About 10 years later they were traded back
to Boeing for new 707 jet airliners.

Juan Trippe Hopes for
Another Double-Decker
Now we fast-forward to the jet age. By
the mid-1960s, Pan Am's fleet included a
number of Boeing 707-320B aircraft for its
long-haul international routes. Mr. Trippe
could see that passenger traffic was booming and these fast and economical aircraft
could make money, even at fares that were
low enough for average travelers to afford.
No longer was air travel just for the wealthy
elite, and Pan Am would soon have to find
some larger aircraft.
Part of this story now becomes autobiographical. In early 1965, as a newly
minted aeronautical engineer, I was hired
by Boeing where I joined a small group
in the aerodynamics preliminary design
department. It was a plum job and a fantastic educational experience.

Stretching the 707
The competitive situation was that
Douglas was developing their stretched
model DC-8-60s, and we at Boeing hoped
to stretch the 707-320B. Two new versions
were presented to the airlines: the 707-620
and 707-820. The 620 would be a modestly
stretched 320B, with more seats but only
domestic-range capability.
The much larger 707-820 was stretched
by 45 to 55 feet over the 707-320B. With
its larger engines, more fuel capacity and
bigger wings, we figured the 707-820 would
carry up to 230 passengers with intercontinental range. But the stretch wasn't going
to be easy. The 707 had shorter landing gear
than the DC-8, so it sat closer to the ground,
and if the fuselage were stretched much
at all, the tail end would be apt to strike
the ground during the rotation on takeoff.
Nevertheless, the sales department made
plastic models of these long, skinny airplanes in the colors of the prospective customer airlines and our preliminary design
group was busy calculating weights, lift,
drag, fuel consumption and range performance. But the most vexing problem was the
runway performance - takeoff and landing - which could only be achieved by a
major redesign of the wing and landing gear
structure because of the tail-strike problem.

We looked at telescoping landing gear
struts. We investigated making the wing
much larger, changing the wing flaps and
slats to get more lift without so much rotation. But every option was complicated and
costly, and while it might have been worked
out somehow, it wasn't long before Juan
Trippe decided he wanted far more capacity than was possible with any stretched
707s. He wanted the passenger capacity
increased to 400, far more than twice the
capacity of the 707-320B.

Starting Over
With the added payload there would
need to be even bigger engines, larger
wings and more fuel capacity. And Trippe
insisted we make it a double-decker by
essentially placing a second 707 fuselage
on top of the original, keeping the conventional six-abreast seating in the upper
and lower cabins. More sales models were
made and painted, and our group went
back to calculating the achievable weights
and performance.
Harking back to Pan Am's earlier days,
Mr. Trippe still had a passion for doubledeckers. He envisioned his double-decker
jetliners taxiing out at dusk with their
two rows of lighted portholes, evoking
the stately departure of great ocean liners
Jetrader * Autumn 2016 59

Jetrader - Autumn 2016

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