Travel maintenace items

[Dan Thomas]

What about non aspirated engines like the O-540 with accelerator pumps? I know the Piper manual calls for priming, which we do, but have seen video's of guys starting various Pipers similar to mine with 3 or 4 fast pumps of the throttle as long as it's not too cold.

With most carbs, a "fast" pump is no better than a slow pump. The accelerator piston is spring-loaded to the plunger rod and it takes maybe a bit less than a second to deliver a complete stroke even if the throttle is banged in.

Whether pumping the throttle or using the primer, it works best if done when the engine is cranking. The fuel WILL accumulate in the intake runner of any engine and eventually drain somewhere. Even the Lycomings with the primer right at the intake valve will drop fuel out the bottom of the airbox if the pilot waits too long after priming before he cranks it. Besides the fire hazard, a delay causes the fuel mist to fall out of the air and end up running down the intake piping, and all the cylinder gets is vapors that are often not rich enough to fire when the weather is cold. Cold air can't hold much water in vapor form, and it can't hold much fuel vapor either. Got to get that mist into the cylinder where the heat of compression will vaporize it into a much richer mix.

Dan

 

[PilotAlan]

What's your experience with failed primers?
... And the leakers only leaked when the primer was moving.

The issue wasn't leakage, it was inability to prime.
I've been nearly stuck twice with primers that either got stuck, or wouldn't develop a vacuum to push a charge to the primer nozzle.
In one case, I could rotate the primer plunger and find a spot where I could get a fraction of a stroke and got the engine started.
The other, I was able to get enough leverage to push the plunger back in, and the engine was warm enough that I could get it started. If it had been cold, the outcome would have been different.

So, my experience may be outside the norm, but it was enough for me to carry a primer kit (two tiny o-rings and a small thing of fuel lube) and two small wrenches to be able to fix it in the field.

 

[Dan Thomas]

The issue wasn't leakage, it was inability to prime.
I've been nearly stuck twice with primers that either got stuck, or wouldn't develop a vacuum to push a charge to the primer nozzle.
In one case, I could rotate the primer plunger and find a spot where I could get a fraction of a stroke and got the engine started.
The other, I was able to get enough leverage to push the plunger back in, and the engine was warm enough that I could get it started. If it had been cold, the outcome would have been different.

So, my experience may be outside the norm, but it was enough for me to carry a primer kit (two tiny o-rings and a small thing of fuel lube) and two small wrenches to be able to fix it in the field.

There's a shortcoming somewhere in the scheduled airframe inspection process. Sticky primers should get fixed then. Primers with worn O-rings should get fixed then. These problems don't suddenly develop; they're a result of age or wear, usually, or because someone lubricated the O-rings. That's guaranteed to cause trouble, and the bore needs to be completely cleaned of all sludge and other garbage.

Much more often people get stuck with mags that won't fire on startup because the points are so eroded and the internal timing therefore off because the proper preventive maintenance didn't happen. Seen this too many times. Alternator brushes wear and the thing eventually stops charging and the next flight can't happen because the battery's too low. Such problems arise out of the same neglect that causes primer failure, but far more often.

Dan

 

[SoloEqs]

There's a shortcoming somewhere in the scheduled airframe inspection process. Sticky primers should get fixed then. Primers with worn O-rings should get fixed then. These problems don't suddenly develop; they're a result of age or wear, usually, or because someone lubricated the O-rings.

Of course, it helps if your A&P actually understands how airplanes work, unlike one who came to do a prebuy on a Stits Playboy that I'm selling. He marked the primer down as inop -- but once I opened the fuel valve, it worked perfectly!

A mechanic might miss a marginal primer during an inspection, so it's important for the pilot to keep an eye on things like this.

 

[kontiki]

By the time one carries enough spare parts along there's no room left for occupants or fuel or bags. Better to keep components current. 500-hour inspections on the mags and alternator will prevent 80% of the likely problems, since most problems tend to be electrical. If a tire is losing air, fix it. A leak will only get worse, and can get worse in a real big hurry. Oleos can go flat without warning and leak oil everywhere, but they're usually full of old O-rings that should have been changed long before. Same for brake master cylinder and caliper seals. They'll leak or fail suddenly much more readily in cold weather.

Dan

[FONT=&quot]I agree with this. [/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]There are really two ends of the spectrum. Replace or overhaul parts, on condition or on time. If you wait until failures, expect inconvenient service interruptions that can offset any maintenance savings. [/FONT][FONT=&quot]If you do everything on time, it can be expensive.[/FONT]

 

[SoloEqs]

[FONT=&quot]I agree with this. [/FONT]

[FONT=&quot]There are really two ends of the spectrum. Replace or overhaul parts, on condition or on time. If you wait until failures, expect inconvenient service interruptions that can offset any maintenance savings. [/FONT][FONT=&quot]If you do everything on time, it can be expensive.[/FONT]

I do oil changes based on time. Pretty much everything else, it's based on condition. Why replace good parts, just because of a set of numbers on a piece of paper? After all, we won't keep flying BAD parts, just because the numbers on paper say they should still be good!

 

[Dan Thomas]

I do oil changes based on time. Pretty much everything else, it's based on condition. Why replace good parts, just because of a set of numbers on a piece of paper? After all, we won't keep flying BAD parts, just because the numbers on paper say they should still be good!

When it comes to things like mags or alternators, you don't have to replace them. There are published instructions for internal inspections that don't really take that long, and at the end of it all it will save money if you're in the habit of going places. If all you do is local flying it's not such a big deal.

Some owners will make a lot of noise about the cost of component inspections, but when they're stuck 400 miles away they end up paying more for motels and meals and cabs and might lose pay for missing work because they couldn't get home. If the place you're stuck is some little backwater airport you might also pay for a mechanic to come out and troubleshoot the problem, then drive back and get the parts (or have them shipped in) and then more time to install them. Maybe the mechanic's meals and motels, too. It can get a lot uglier than 500-hour mag or alternator inspections.

Dan