Engine NewsTechnical Corner

New feature on ULPower engines : Integrated by-pass unit

As part of  their continuous development and devotion to their concept “Easy to install”, ULPOWER has designed a built-in by-pass solution which will be installed as standard equipment on all new engines. (May 2019).

Field experience shows that certain aircraft fuel systems may, under certain conditions, allow varying amounts of air to enter the fuel supply lines (empty tanks/switching tanks, unporting of tanks, etc); this appears to be one of the most common reasons for engine stoppages. If at some point in flight, sufficient air is ingested to the system, the pressurised fuel lines will need to re-prime with fuel, displacing the air. The more air that is in the lines the longer it will take to clear and return to normal running.  Air over the injectors at the time of opening will result in loss of power and/or engine stoppage.  The most common solution for this issue is to install a restricted by-pass unit between the pressurized fuel supply line and the fuel return line.

Devoted to their “easy to install” concept, ULPower has now designed a fuel injector block with integrated by-pass – eliminating the need for ‘external plumbing solutions’ to achieve similar results.             

It should be noted that the fuel pumps used in a ULPower installation are more powerful than found on most similar engines, and these help to clear air pretty fast already, so we expect that the integrated orifice will now make priming even quicker – giving ULPower an ever greater advantage!

This new design will not only be installed on all new engines leaving the ULPower factory (May 2019), the good news is that the integrated by-pass solution may also be retro-fitted on older engines.  The fantastic pictorial guide for the change procedure can be downloaded here . RETROFIT AN INJECTOR HOLDER WITH INTEGRATED BYPASS  


The integrated by-pass kits (K1100001 for  UL260/350 and K1100002 for UL390/520) can be ordered through your local ULPower dealer who can also assist you if you are feeling unsure about performing this procedure.

It should be noted that it is NOT acceptable to install an external restricted orifice if you have the integrated unit installed…. so look for the ‘dot’ on the ‘integrated’ injector block/regulator unit.  If there is a ‘dot’ you should NOT add an external unit.  If there is no ‘dot’ you may, optionally install a unit.

Once again, we are pleased to see the excellent engineering solutions that come from ULPower being implemented to keep engine installations simple, clean and appropriate for the homebuilder and other non-certified aircraft out there.