Almost every aircraft out there has something that makes it unique
and special. Some of these are easy to spot and are visual identifiers of a particular aircraft,
while others are performance related and might only experienced by pilots and crews.
In today’s video we’ll go over 10 different quirks of various Airbus and Boeing jets that you may not
know about - especially if you haven’t yet checked out our main Simple Flying Channel!
Are you ready? Let’s begin!
#1: The Eyebrow Windows on some Boeing 737s.
If you look above the cockpit windows on the Boeing 737, you may see an extra set of smaller,
thinner windows. These are ‘eyebrow windows’ and were once a useful addition for aircraft
navigation and maneuvering. Advances in technology have seen them phased out,
but you can still see them in place on some older aircraft.
Installed on up until the early 2000s, these eyebrow windows were a common appearance on
early Boeing and Douglas aircraft, including the Boeing 707 and 727.
The main use of these windows was to aid visibility outside the cockpit, allowing for
extra visibility during turns, particularly tight turns when approaching airports.
With advances in technology, eyebrow windows started to become less useful. Navigation of
course now is computer and satellite aided, rather than visual. And whilst clear vision
is always going to be important, advances such as improved instrument landing systems
and traffic Collision Avoidance Systems made them less necessary.
#2: The mask around the windscreens of newer Airbus jets.
Sticking close to the cockpit, one of the most distinctive aspects of the new Airbus aircraft is
the black ‘mask’ or visor around the windshield. Starting from the A350, new models like the
A330neo and A321LR and beyond have featured this. While the dark outline certainly looks striking
and unique, the reason for having it is not just aesthetic. According to Airbus,
“The emblematic “sunglasses” like black windshield eases the window’s maintenance and contributes
to harmonising the thermal condition of this temperature-sensitive window area.”
Put simply, this means the black color adjusts better to the temperatures surrounding the
aircraft. Planes routinely go through rapid temperature changes, taking off
from hot airports in the cold atmosphere, and all parts must adjust to this change.
As far as we can tell, however, similar designs on Boeing jets that are part of the liveries of
Air Canada and Northern Pacific, are purely aesthetic. … They look good though…right?
#3: The A330-200 freighter’s nosegear lump The A330-200F has a rather unusual feature – a
blister-like lump just forward of the nose gear. To explain its presence, its important to know
that the freighter was never designed from the ground up to be a cargo plane,
and so it required some modifications to make it suitable for the role.
The passenger-carrying A330-200 entered into service with Canada 3000 in 1998,
four years after its larger brother, the A330-300 began flying commercially. It was
more than 10 years before the freighter took its first flight, ahead of entry into service in 2010.
The nose-down pitch of the A330 family, something it shares with the A340, meant
it was impossible to achieve a level cabin floor – something that was essential as a cargo jet.
To overcome this issue, Airbus was forced to redesign the landing gear for the
freighter variant. FlightGlobal notes that the manufacturer studied several options for this fix,
including adding a longer nose gear leg that articulated to fit into the existing bay profile.
However, this would have affected the commonality with the passenger fleet,
something that has long been a big selling point for Airbus.
So in the end, it settled on lowering the leg attachment points to raise the nose slightly
when the aircraft was parked. This modification required a larger gear bay to house the nose gear,
which required some additional housing –and hence the bulge.
#4: The Boeing 737’s uncovered wheels If you look at the underside of the Boeing
737 shortly after takeoff or in flight, you will see that the main landing gear wheels sit
exposed after folding into their housing. On most other aircraft, it is covered by closing doors.
This related to a design issue that dates back to the first 737-100, introduced in 1968. The
aircraft was designed to be low to the ground- a choice to make the 737 more usable at smaller,
regional, or remote airports. Keeping the aircraft lower to the ground would make it much easier to
load passengers and cargo and also to service and fuel the aircraft with limited equipment.
But with the fuselage kept lower to the ground, there was no room for landing gear doors.
These require extra clearance when operated and could come into contact with the ground.
Removing the doors, though, was not necessarily a bad thing.
It is one less mechanical item to be repaired and maintained. And it reduced
the overall weight of the aircraft and freed up vital space in the belly of the aircraft.
Adapted to their high-altitude exposure, wheels have smooth hubcaps on the external-facing side,
which aids aircraft aerodynamics. There is also a rubber seal around the fuselage opening,
which helps prevent any objects, or water, entering the landing gear enclosure.
#5: The Boeing 787’s curved wings. One of the type’s most iconic features,
the swept-back nature of the Boeing 787’s curved wings results in the aircraft having
what are known as ‘raked wingtips.’ This also functions as an alternative option to winglets
and contributes to increases in both fuel efficiency and, consequently,
operational range. There’s also a reduction in vortices that develop at the tips of the wings.
Boeing also notes that “The use of composite materials in the wing structure allows the 787
wing to have a higher aspect ratio (the square of the wing span divided by the wing area) than
previous aircraft.” The result of these various features
is something of a perfect combination for the Dreamliner’s operators. Due to its abundance
of technology, it can fly faster than its predecessors, while consuming less fuel.
#6: The serrated engine covers on some Boeing jets
In addition to acoustic liners, Boeing says that these chevrons are such effective noise
suppressors that several hundred pounds of sound insulation may be eliminated from the fuselage.
The reduced weight translates to greater operational efficiency for airlines.
A 2005 Boeing Frontiers article discusses this feature, saying:
“To combat the sound of jet-blast from the rear of the engine, Boeing, General Electric,
and NASA developed serrated edges called chevrons for the back of the nacelle and the engine exhaust
nozzle. The chevrons reduce jet blast noise by controlling the way the air mixes after
passing through and around the engine.” It looks to be a useful feature. But on
the other side - why don’t Airbus jets have them? On the one hand,
it appears that Boeing is the holder of the patent for part of this design (or a variant of it).
However, an interesting message thread on Stack Exchange shows a 2006 FlightGlobal article stating
that the chief engineer for the Airbus A350 decided against chevrons. Apparently, the team
didn’t get a noise advantage from this design. Combined with a specific fuel consumption penalty,
the aircraft designers decided not to adopt them. With improvements in noise insulation technology,
it might explain their absence on the upcoming Boeing 777X as well…
#7: The non-circular shape of Boeing 737 engines You may or may not have noticed that
modern-generation 737 engines have engine casings where the bottom flattens out,
rather than continuing around the same circumference to complete a circular shape.
As engine technology improved, engineers discovered that the more air an engine could
suck in, the more efficient its operation will be. For an increased air intake, engines need
larger turbines powered by larger fans. These require a suitably-large engine casing to fit.
However, it was quickly discovered that larger and more efficient engines wouldn’t fit with the 737’s
low-to-the-ground design. Engineers looking at the aircraft realized that the engines’ casing,
rather than the size of the powerplants as a whole, could be modified. As such,
they needed to find a shape that was not purely circular. This would prevent the
engines from hitting the ground, even if they were larger than previous models.
#8: The absence of reverse thrust on two of the A380’s engines.
When the A380 was first designed, there was a debate about whether the plane would feature
reverse thrust at all. These superjumbos are designed to come to a complete stop using their
brakes alone. Ultimately the decision was made to put reverse thrust on two engines
to help minimize the risk of aquaplaning. But it was also decided that four reverse thrust on all
four of the A380 engines was definitely overkill. So the first reason why the A380 only has reverse
thrust on two inside engines is because that’s all it needs. Further reverse thrust is surplus
to requirements and simply adds to the plane’s overall weight and puts more stress on the wing
structures. In fact, adding reverse thrust to a single A380 engine adds half a tonne of weight
to the plane. Given a fully loaded A380 weighs up to 1,265,000 pounds and is already expensive
to operate, no-one is in a hurry to load the aircraft up with more weight than necessary.
#9: The barking dog noise on certain Airbus jets. Passengers on the A320 and A330 can expect to
hear a barking noise emanating from the plane at some point during their flight.
This noise, which has also been likened to a buzzsaw,
is actually caused by a hydraulic pump which is referred to as the Power Transfer Unit,
or PTU. The location of the PTU means that the barking dog sound is most likely to be audible
for those seated in proximity to the wings of the aircraft, but it is loud enough that often others
in less adjacent seats can also hear it as well. Unusually for a pump system, most of which are
powered electrically, the PTU is hydraulically powered. The purpose of the system is to ensure
that minimum pressure is maintained across the hydraulic systems of the aircraft. This system
produces the quote-unquote ‘barking dog’ noise that is associated with certain Airbus jets.
#10: Toilets in the cargo hold of some A340s. The Airbus A340-600 has a massive amount of
space- both in the main passenger cabin and below it, in the cargo hold. With all that space in the
cargo hold, Lufthansa was faced with a choice when selection options for its larger A340s.
It could try to fill up the jets with cargo for each flight (and potentially
leave with space that it can’t sell), or move the toilets downstairs, and place more economy
class seats where lavatories could have been. Lufthansa chose the latter and relocated the
toilets downstairs, thereby increasing the number of passengers onboard the aircraft.
More than just toilets, this downstairs section also accommodates an extra galley for food
and beverages. Carts loaded on the lower level are moved up using a small elevator.
We hope you’ve enjoyed this little compilation and explanation of various aircraft features.
What is your favorite quick on a commercial aircraft? Share it with us by leaving a comment!