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ROTORwrench…Tips, Tricks, and Info - December 2017

Posted 6 years 164 days ago ago by Scott Skola

Helicopter Maintenance Blog* 
November 2017

Well, we made another year. Thanks for your support.

Next year, I plan to expand the “daily preflight check” format we’ve been using with the Lama tips to other airframes. Will probably start with a 407 or AS350 before I lose those memories too…

We still have a few more Lama tips to share and will interject those along with other daily tips throughout the year.

And keep your emails coming. If you have any questions, tips to share, or have a topic suggestion just shoot me an email. 

Till then…

Airbus (Sud Aviation)
SA315B Lama

Continuing with the Artouste IIIB1 start system anomalies.

Next most common fault with an engine start is a normal light sequence, but the engine hangs or accelerates slowly, or aborts. Likely this is a faulty igniter, lead, or coil. To discover which one it might be, disconnect the C3 connector (starter) at the control box to take the starter off line. We are going to conduct a “simulated start.” 

WARNING: A “torch igniter” is a fuel atomizer that sizzles and ignites a flame. The flame is like an Oxyacetylene torch with just the acetylene ignited, very soft and sooty. The flame warms the combustion chamber before the main fuel arrives. 

NEVER conduct the simulated start with both the ignition coil AND the Micro-Pump plugged in, you’ll operate a torch igniter inside the engine at static, not good. 

For our test, disconnect the Micro-Pump plug and remove the fuel lines from the torch igniters, but keep the igniters connected to their electrical leads. Hang the igniters off the side of the engine where you can see them. 

With the battery ON, hit START and see if both igniters sizzle. If one does not sizzle, swap the igniters from one side to the other, then the electrical leads, until you identify the bad part(s). It may be a bad igniter, a bad lead, or one bad side of the coil output. 

If you have one good igniter, one good lead, and one good output of the coil, put them on the same side and see if the engine will start on one igniter. Some engines will, but very slowly. Others will hang, time out, and abort. Good luck. 

But if you are in a situation where you really need to start the helicopter and you determined one side of the coil is bad, go for a live start and tap on the coil with a rubber mallet during the start sequence. Coils have been known to get a piece of grit in one of the breaker points sets and tapping might dislodge it. 

Artouste start components are only guaranteed to function correctly above 14V. A component that works at 24V during a simulated start with the starter disconnected, may not work with the starter load on line at 14-15V. The simulated start is used to detect a defective component at 24V which follows that the component will also be defective at lesser voltages. 

A true function test must be done with the starter on line and only one, the Micro-Pump OR the Coil plugged in, depending on whether you’re troubleshooting a fuel or spark problem, and in accordance with the warning mentioned earlier. 

This troubleshooting technique, the simulated start, can be used to test any individual electric component of the engine start system. Let’s say the start circuit breaker is popping on every start a few seconds after START is selected. Isolate by disconnecting the electrical plug from all start accessories but the one you’re testing. 

Test each individual component until you find the one that pops the breaker: Starter Relay, Micro-Pump, Coil, Start Valve, Main Electric Fuel Cock (EFC), or Boost Pump (remember the Boost Pump is on automatically during start selection, whether it is switched on separately by the Boost Pump switch, or not).

The only time you would have the Micro-Pump plugged in and the Coil disconnected is if you’re testing the Micro-Pump functioning. A start light sequence with a GREEN starter light, starter engagement, and no YELLOW light would require this test. 

Remember the YELLOW light indicates that the Micro-Pump has provided fuel under pressure to its pressure switch, which trips, lights the YELLOW light and also sends this same current to the EFC to open and admit main fuel for start. [Submitted by Lama-Nator]


Leonardo/AgustaWestland Newsletter Winter 2017:

SUBMITTING MAINTENANCE TIPS/TRICKS/QUESTIONS/INFO: Have an old tip or trick you’d like to share with your fellow mechanics? Or maybe a question that you can’t seem to find an answer to? Or just some info to pass on?  Send an email to: [email protected]

About the author: After 32 years maintaining helicopters in various capacities, Scott concluded a full time career with a major operator in 2014. When not pursuing future writing projects, he can still be seen around the flight line tinkering on aircraft for beer money. 

*To keep the hounds at bay, the information contained in this blog is for discussion purposes only.