The Boeing 747SP is certainly one of the most unique looking airliners ever built.
This shortened version of the Boeing 747-100, named the 747SP
for “Special Performance”, was developed in the 1970s as a longer-range 747 variant.
At the time, Boeing had a bit of a gap in their product line between the
160-seat 707 and the 350+-seat 747. Back then, McDonnell-Douglas and Lockheed were
both vying for that segment in between with the DC-10 and L-1011, respectively.
In order to compete, and to cater to a request by Pan Am and Iran Air for an
extra-long-range airliner that could carry around 280 passengers, Boeing’s solution was the 747SP.
Officially launched with a 10-plane order from Pan Am, the 747SP is roughly 50 feet shorter
than the original 747, and could fly nonstop from New York to Tokyo with plenty of fuel to spare.
Ultimately though, only 45 of these planes were ever built, and with the last one delivered in
the late 1980s, you can imagine it’s a pretty rare aircraft these days. Of those 45 planes,
only four of them are still flying on a regular basis, at the time of uploading this video.
So, given all that, it may surprise you to hear
that there are two of these planes still flying in Canada.
Charlie Foxtrot Papa Alpha Whiskey and Charlie Golf Tango Foxtrot Foxtrot are two
Boeing 747SPs that first flew in 1976 and 1980, respectively. ‘PAW’ was originally delivered
to the Civil Aviation Authority of China, while ‘TFF’ started its life with Korean Air.
Today, they both fly for Pratt and Whitney Canada, and what’s more,
these two 747SPs are also the very last 747s on the Canadian aircraft register.
PAW first started flying for Pratt and Whitney in 2001 under an American registration,
and was then switched over to its current Canadian one in 2009.
TFF joined Pratt and Whitney in 2008 before being moved to the Canadian registry as well in 2010.
Given who’s flying them, the purpose of these 747SPs is pretty clear - they serve as engine
testbeds for Pratt and Whitney, and are based out of Montreal-Mirabel Airport in Quebec.
The Pratt and Whitney Canada Mirabel Aerospace Centre first opened in 2010,
and supports flight testing for the entire range of Pratt and Whitney engines.
The facility was built with two huge hangar bays to house both 747SPs, and with two long
runways and limited traffic, Mirabel Airport was deemed the ideal base for these testbeds.
Now, obviously, new aircraft engines under development have to undergo a rigorous testing
program before they’re certified, and a big part of that is testing an engine in flight.
PAW has a modified #2 engine pylon where larger, in-development engines can be fitted,
while TFF has a very unique fifth engine pod on the upper right side of the fuselage.
This 5th engine sits on a small wing that doesn’t create any extra lift,
since it would affect the rest of the aircraft’s flight characteristics. That allows them to test
smaller engines and keeps them away from any disturbed airflow around the nose.
But the question still remains - Why 747SPs, of all planes?
Well, I did reach out to Pratt and Whitney and they didn’t exactly get back to me,
but there are a couple reasons out there as to why they use these planes.
First things first, when testing large aircraft engines in flight, you do generally
need a four-engined plane for stability and safety purposes. If you’re swapping out the #2 engine for
testing, there’s a good chance it has a different amount of thrust than the other three do.
So, by adjusting the thrust on the opposing engine, and using the remaining two to maintain
altitude and airspeed, you can avoid this asymmetric thrust, unwanted yaw,
and a flight profile which might not give accurate data.
There are exceptions to that like TFF’s 5th engine pod
and Honeywell’s 757 which also has a side-mounted pod,
but those are for smaller engines which have much less thrust compared to the others.
For the larger engines though, this type of flight testing isn’t exactly
the sort of thing you do by replacing one of the engines on a twinjet.
For the 747SP in particular, it reportedly has an “excellent flight envelope”,
with very stable and predictable flight characteristics. Because of that, it also
allows for the “largest selection of flight parameters that [Pratt and Whitney] can get”,
by testing these engines at a wide variety of altitudes, speeds, outside temperatures, and more.
It’s also worth mentioning that when Boeing shrunk the original 747 to create the 747SP,
the overall weight of the aircraft decreased substantially,
but the power stayed largely the same, making the SP quite the performer.
That extra performance could very well play a role when using the SP for engine testing by
adding an even greater safety margin, especially when they’re flying with only 3 original engines.
Also, it’s reasonable to assume that low acquisition costs played a role
back when Pratt and Whitney first acquired them,
since they would have been 25 and 28 years old back in 2001 and 2008, respectively.
The acquisition costs are only part of it today though, since these planes have
now been very extensively modified for Pratt and Whitney’s purposes.
Reportedly, the cabins of both planes are effectively airborne laboratories, having been
fitted with workstations throughout, and only the nose sections keep some of their airline heritage.
There is no doubt a considerable amount of investment that goes
into bespoke testing aircraft like these.
Given that, it doesn’t seem to be a simple matter of replacing the SPs with, say, newer 747-400s.
Even then though, these two planes are now over 40 years old, and with them making
up half of the remaining fleet of flying 747SPs worldwide, they’re rarer than ever.
According to Skies Magazine back in 2019 though, the two aircraft have relatively
low cycles and only fly for around 250 hours a year each. As a result, they’re kept in,
quote, “impeccable condition” and could keep flying for another 20 years.
In a similar way, GE’s own 747-100 testbed was the very last 747-100 flying,
up until its retirement in 2017.
So, long after the last private airframes are retired, and NASA
unfortunately ends their flights with SOFIA, it’s entirely possible that
Canada’s last two 747s may just become the last 747SPs flying in the world.
Thank you all so much for watching,
to my good friend Mark Brandon for the extra footage, and I’ll see you next time.