# What defines a landing gear bogie?

(Wikipedia) A Boeing 737 main landing gear arrangement.

What defines a landing gear bogie (truck)?

In its airframe maintenance handbook, the FAA defines it as:

When more than two wheels are attached to a landing gear strut, the attaching mechanism is known as a bogie.

But, they go on and describe the Boeing 777 main landing gear (MLG) as:

A triple bogie main landing gear assembly.

That means each lateral pair of wheels is a bogie, which is what the undercarriage arrangements Wikipedia article calls a 2-wheel nose landing gear.

For me, a bogie is when a strut holds a longitudinal arrangement of wheels (like trains). For example, the MLG of a Sukhoi Su-34 (shown below) would be a bogie, but not a Boeing 737 MLG, despite both having two-wheels each.

Are there technical terms to distinguish the two images shown in this post?

• I believe “triple bogie” should be read as “bogie that is a triple” (i.e. has three axles) rather than as “three bogies”. – Jan Hudec Jul 26 '17 at 17:24
• A triple bogie is three over par. :P – TomMcW Jul 26 '17 at 18:15
• @TomMcW +3 for you. – ymb1 Jul 26 '17 at 18:20
• This is known as a birdie. Good thing it wasn't an eagle – TomMcW Jul 26 '17 at 18:23

The term bogie initially meant (atleast in Britain) an assembly of wheels forming a pivoted support at either end of a railway coach, which provided flexibility on curves.

So, the term bogie refers to the set of wheels, rotating about the (landing gear) axis, while their arrangement- lateral or longitudinal doesn't matter.

An old patent for Bogie undercarriages for aircraft notes:

... a bogie having multiple wheel assemblies mounted on transverse rotational axes spaced one behind the other ...

The issue is that the term has been in use for a long time an has come to mean a number of things (even in railways, the entire carriage can be called a bogie)- so while the correct term is to call it a four (or six) wheel bogie rather than double or triple bogie, it is used quite often. Also, as I already noted, whether it is lateral or longitudinal doesn't matter as long as they are attached to the same (nose or main) gear.

• @ymb when I said already noted, I was referring to my statement in second para, not that in the patent. – aeroalias Jul 26 '17 at 16:56
• as shown below Is there supposed to be an image? – TomMcW Jul 26 '17 at 18:20
• @TomMcW I think "shown below" refers to the quoted text. – FreeMan Jul 26 '17 at 20:02
• @TomMcW I've edited it slightly. Hope it makes better sense now. – aeroalias Jul 27 '17 at 0:09