Kevlar Ultimate Fuel Buffer High Altitude series.

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  • Regular price $399.00

 This is a military spec light reinforced device that functions as an air trap and fuel buffer system for Stratospheric/ Space Unmanned Aerial Vehicles.

It is designed and assembled in the USA by Ultimate Jets from certified  MIL spec components and derived from a unit that complies with MIL-STD-810G parts 513.6, 514.6, 516.6 and 520.3.

This device also fulfill a series of specific requirements for high altitude/ very low temperature operations.

The device is tested to 2 bars pressure and -40c service conditions.

Stratospheric/ space vehicles with multimode engines and re-entry capabilities have very specific requirements on fuel tanks to avoid venting the landing fuel into vacuum while in space. These requirements are fulfilled by these units.

The UFBK series are constructed from pressure molded monocoque kevlar tanks and Al 6061 screw type stopper assembly as well as PEEK 3D printed vibration and shock absorbing mount. The manufacturing process of the machined and 3D printed parts is certified to a high precision of 50 micrometer or 0.0020". 

The kevlar tank is pressure molded in an aluminum mold and cured in a high temperature autoclave.




The units are sized to be useable with jet engines from 1000 N of thrust to 5000 N of thrust class. The ref number of the UFB relates to its max rated thrust.

We recommend setting it up according to the Industry best practices.


The advantages of this air trap compared to other products on the market:

1. Very high strenght-to-weight ratio.

2. High buffer capacity offering large air retention capability and very low suction drag.

3. Fully serviceable with large fittings that can be ordered/ swapped to the customer requirements. Filter is replaceable and available here.

4. Superior resistance to cavitation/ vacuum conditions

5. Extremely high manufacturing quality and resistance. Superior resistance to vibration thanks to its unique 3D printed mounting system.

6. Pressure tested to 2 bars

7. Very strong mounting solution and overall design.

8. Designed for strtospheris UAV and space vehicles. 

As a reminder, the main reason for fitting an air trap in the fuel system is to cater for the non perfect clunk pickup. No matter how good the clunk system is setup, you will always end up sucking some air while emptying your tank. Especially towards the end of the flight when the tank empties and while performing aerobatic maneuvers.


In-flight fuel tank video from Oli Ni on Vimeo.


 In the video above, which demonstrate what happens to the fuel in the tank during aerobatics, the clunk is out of the fuel for 50% of the time, picking up air that will be sent to the air trap during this period.


1. Primarily, The air trap is here to buffer that amount of air and prevent it from entering the pump ( which would cause a flameout condition ). On this respect I strongly recommend fitting an air trap that volume equals to 30 seconds of consumption at full thrust.

2. The second function of a modern air trap is to protect the system against cavitation. For this, the fuel membrane must have two qualities: 

    a. Offer low restriction

    b. Being able to suck fuel even when largely uncovered and in the air


The 3 sizes will allow you to comply to the 30 seconds rule up to 5000 N engine class. The unmatched and proven quality of their membranes will get you the best resistance to cavitation on the market.

Technically speaking air trap consists of an aluminum screw type stopper CNC machined , a MIL spec kevlar tank and a bespoke super fine fuel filter membrane. 


Ultra large 16/ 14/ 10 mm MIL spec Pisco fittings can be specified on all the sizes.




1000 for max 1000 N thrust engines




2000 for max 2000 N thrust engines


5000 for max 5000 N thrust engines.