What are ATLAS and KSSU standards?⌗

There are different unit standards in aviation industry. The currently most widely used is the ATLAS standard. It’s name comes from the European Airline Alliance, which has agreed in the 1960s on a uniform standard for their aircraft components, maintenance processes, operational planning and training programs. The founding members of the ATLAS standard were: AirFrance (A), UTA (T), Lufthansa (L), Alitalia (A) and Sabena (S). Due to its widespread use by approximately 80% of all airlines it can be considered as a future standard.

Along with the ATLAS standard, another common one is the KSSU standard. Visually, they look almost identical and differ only slightly in their dimensions, but are not fully compatible. The KSSU standard was introduced by these airlines: KLM (K), SAS (S), Swissair (S) and the French UTA (U) in the early 1970s.

Problem sourcing spare parts⌗

I’m currently a proud owner of two beautiful airline trolleys. One is from Lufthansa and a ATLAS standardized service trolley. The other is a KSSU trolley from Austrian Airlines. Recently, unfortunately, material fatigue occurred in one of the rollers under the KSSU trolley. Although the rollers are made of nylon, a very robust material which can cope very well with high mechanical stress, the trolley was used since 2004 until recently by Austrian under certainly harsh conditions. Since the rollers are held in position by a riveted hardened metal pin, there was no way around replacing the entire roller system. Unfortunately, I was not able to purchase replacement castors for the KSSU Standard. Fortunately, ATLAS and KSSU castors are very similar in design and differ only significantly in the spacing of the boreholes.

One adapter to combine both standards⌗

So with the help of an adapter it would be possible to overcome this hurdle and even keep the entire braking mechanism functional. Due to height differences, all four rollers must be replaced for this modification. After thinking about it for a while, I decided to use PLA as material for practical reasons and to shape it with the help of a 3D printer. Thanks to the possibility of embedding a honeycomb structure in the workpiece, very good torsional stiffness and compressive strength can be achieved.

Sliced Models Honeycomb Structure
Sliced Models Honeycomb Structure

Interactive 3D Model⌗

The first revision of the adapter was designed by the engineering student Beatrice Lühring and is shown below. This is screwed onto the ATLAS castor and four 16mm M5 countersunk screws sink precisely into the adapter.

The center recess is for the brake mechanism. The adapter and castor are screwed to the KSSU trolley using the four outer screws.

Assembly of the roll mechanism⌗

In the picture below you can see the already disassembled damaged castor. The nylon roll is broken and has already been trashed.

Broken Castor Housing
Broken Castor Housing

The brake rod is shifted vertically depending on the pedal position. This presses the brake shoe in the castor onto the rollers and locks them in place.

Break Rod
Break Rod

On the left you can see the new castor with the adapter. On the right the old castor in a very bad condition.

Old/New Castors Side-by-Side
Old/New Castors Side-by-Side

Fully assembled and shortly before the first function test. Especially the small distance between the front rollers and the pedals is concerning.

Fully Assembled Bottom
Fully Assembled Bottom

Result⌗

The result looks remarkable good.

Fully Assembled Trolley
Fully Assembled Trolley

Errata⌗

  • The distance between two drill holes for the KSSU screws of the ATLAS castor is so small that no washers can be used there.
  • The front rollers can collide with the brake pedals of the trolley during a full turn. If this happens, a piece of the brake pedal must be shortened to prevent this.