TCM Fuel System

Tips on inspection and setup of TCM continuous flow fuel injection systems.

Fuel system inspection is an important part of inspecting Teledyne Continental Motor (TCM)-powered aircraft. It is vital to ensure the continued safe operation of your customers’ aircraft. But some mechanics aren’t performing these inspections properly. Some may not even be doing the inspection. For this month’s article, AMT sat down with Don Fitzgerald, director of training for Teledyne Continental Motors, to get tips on proper inspection and testing of TCM fuel systems.

Let’s go ahead and start off with a disclaimer. This article is meant to complement the technical information provided by Teledyne Continental Motors, not take the place of it. Always refer to the manufacturer’s maintenance manual and applicable service instructions when inspecting and setting up the TCM fuel system. Service Information Directive (SID) SID97-3 is the document that covers procedures and specifications for adjustment of TCM continuous flow fuel injection systems. The current revision of SID97-3 is “D.”

That covers my disclaimer. Now let’s look at TCM’s. If we read the first paragraph of SID97-3D, we see the following statement:

“Warning. The procedures and values provided in this service bulletin apply to TCM fuel-injected engines that have not been modified from their original type design. Refer to supplemental type certificate (STC) holder information and instructions for aircraft and engines that have been modified from the original type design.”

If you have an STC involving components or accessories to the TCM engine that affects the original type design, such as adding a turbo-intercooler or turbo-normalizing the engine, that would drastically affect the fuel system requirements and thus render the use of SID97-3D ineffective for the engine. At that point, you should refer to the STC holder’s fuel setup data.

When to perform check
Operational verification of the engine fuel system is required any time one of the following circumstances occurs:

  • At engine installation
  • During 100-hour and annual inspections
  • Whenever a fuel system component is replaced or adjusted
  • When changes occur in the operating environment

SID97-3D spells out the procedures for setting up the fuel system on TCM engines that includes pre-setup, setup, adjustment (if needed), post-setup, and flight test.

Pre-setup procedures
The pre-setup procedures outlined by TCM are an important step. Nonetheless, Fitzgerald shares that many mechanics skip over this important step. “I often find that most folks have the tendency to overlook the section in the bulletin right after the tools and equipment which is the pre-setup procedures,” Fitzgerald tells AMT. “A lot of people just jump from the tools right to the setup procedures. But the pre-setup section covers a lot of things that a mechanic should do during a good 100-hour or annual inspection. All of those items can affect the performance and the way the engine and fuel system will produce the fuel for the engine – especially in turbocharged applications.”

If you are doing the fuel system check because of an engine change or a fuel system component change, the fuel system needs to be flushed. Remove the engine-driven fuel pump inlet hose and terminate the end into a large, clean container. Operate the boost pump and allow a minimum of 1 gallon of fuel to flow through the system. If you notice contamination, locate and correct the source and repeat the fuel system flushing procedure. SID97-3D discusses a more detailed flushing procedure for all IO-240-B engines.

Verify the accuracy of the aircraft tachometer, manifold pressure gauge, and fuel flow gauge.

Remove the engine cowling. Ensure all fuel system components are of the correct part number and are installed properly.

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