Preflight - above and beyond

TMetzinger

Final Approach
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Tim
Obviously, we all (should) do the preflight inspection as given in the POH/AFM. Share with the class what "extra" things you do on a preflight, when, and why.

For me, when I am getting to know a new airplane/FBO, or whenever a plane is coming out of maintenance, I add:
  • Logbook Review
  • Remove the cowling and take a good look at the engine compartment. I've found tools and rags even at "good" shops. If possible I will inspect the airplane at the completion of service before they button it up. The shops that I've done ferry work for are used to this and in fact they expect the guy who's gonna ferry their just-fixed plane to be present for the final stages of maintenance right before the test pilot does his hop.
  • Check every piece of electrical equipment on the airplane (including the ground power connection).
  • Check all control surfaces/cables/pushrods, paying close attention for proper safety wiring, and proper operation (nothing like having your ailerons backwards to wake you up).
 
Check all control surfaces/cables/pushrods, paying close attention for proper safety wiring, and proper operation (nothing like having your ailerons backwards to wake you up).

I thought that was part of the standard preflight. Check fasteners for security and check for excess movement for hinges. Watch the flight control movement while wiggling stuff.

Controls: Don't just wiggle them a little. Move them through the entire range stop to stop. (The Cherokee had some loose wiring after adding new instruments and the flight controls caught on something behind the panel) Check the trim tab for proper operation also. Observing the flight control movement is a given. (I've seen a few people look out the front window while checking free and correct)

Flaps full down. Push up on the trailing edge of the flap and see what happens. Check the control rod attach point. That probably kept me from getting killed in a CE172 one day though it gave the A&P a heart attack. A flap really should not move up 4-5 inches when pushing up on the trailing edge with your hand as you walk under the flap.

After maintenance: Look under the panel for loose stuff. I'll also pull inspection covers off and look inside at pulley's and such. (Our mechanic would leave the covers off for us to snoop in and put on as he walked around the plane with us after an annual. I was stupid back then and wouldn't have thought of that at the time however he insisted we stick our noses and fingers in there and know what stuff is supposed to look like. He also wouldn't give anyone the keys until he flew it himself - good guy)
 
You're right that checking controls for proper operation is part of every preflight. The "extra" I do is to pay close attention to the interconnection - a cable can be off a pulley and the surface will move properly, until it's under aerodynamic load.
 
Controls: Don't just wiggle them a little. Move them through the entire range stop to stop. (The Cherokee had some loose wiring after adding new instruments and the flight controls caught on something behind the panel) Check the trim tab for proper operation also. Observing the flight control movement is a given. (I've seen a few people look out the front window while checking free and correct)

I've also heard horror stories of pilots taking off after their post-maintenance preflight only to find out - in flight I might add - that the ailerons or elevator were rigged backwards - right is left, up is down, etc. Actually watch and THINK about what the controls are SUPPOSED to be doing.
 
I've also heard horror stories of pilots taking off after their post-maintenance preflight only to find out - in flight I might add - that the ailerons or elevator were rigged backwards - right is left, up is down, etc. Actually watch and THINK about what the controls are SUPPOSED to be doing.

To paraphrase Sherlock Holmes: Most people look, but they do not observe.
 
when checking the ailerons, I say, out loud "Towards me, up....away from me, down."

When the aileron goes up, the yoke turns towards me. The day it doesn't, is the day I don't fly :D

Also, I noticed that a lot of people do not check the tension in the belts. I always check the tension in any belt I can reach.
 
You're right that checking controls for proper operation is part of every preflight. The "extra" I do is to pay close attention to the interconnection - a cable can be off a pulley and the surface will move properly, until it's under aerodynamic load.

I have found regulary flown airplanes that had serious control issues doing good control checks.

I found Commanche that would lock the ailerons when the control yoke was full forward, I.e. you could not turn the yoke with it full forward.

I also found a C-172 that would pop a circut breaker every time you move the yoke full forward and turned it.

I have also found a Sailplane that had the ailerons hooked up backwards, This is very strange and harder to catch than you might imagine. Fortunately I was suspicious to begin with as it had had some major work done on the controls.

Brian
 
i always do a positive control check after assembling my glider. make sure all control circuits are hooked up and properly functioning by moving the stick while someone else provides resistance at the control.

there was a V tail glider here in Ames that crashed and took down a towplane about 15 yrs ago thanks to the ruddervator not getting hooked up, period. when the pilot moved the stick about the ruddervator still moved, because the pushrods were bumping up against the control ends at the tail, but there was no connection. thankfully both pilots lived.
 
Obviously, we all (should) do the preflight inspection as given in the POH/AFM. Share with the class what "extra" things you do on a preflight, when, and why.

I pull my engine thru 4 blades, guess why?
 

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Gravity and oil

Radial engines are dry sump engines there should be no oil left in the engine case. The scavenge pump should have removed the oil and returned it to the oil tank.
 
when checking the ailerons, I say, out loud "Towards me, up....away from me, down." When the aileron goes up, the yoke turns towards me. The day it doesn't, is the day I don't fly :D
Also, I noticed that a lot of people do not check the tension in the belts. I always check the tension in any belt I can reach.

I always do the thumbs up check when checking free and correct. Yoke turned left thumbs are up and pointing left so that aileron on the left should be up and reverse for right side. I can't remember where I heard it but I always follow that routine.
 
Radial engines are dry sump engines there should be no oil left in the engine case. The scavenge pump should have removed the oil and returned it to the oil tank.

Good to know - I'd swear I'd heard of this with radials, though. Or is it a check that the scavenge pump actually did the job?

Anxiously awaiting the "correct" answer for the pull-through.
 
Gary, I do that too,.. Lee taught me that on my first flight with him to Lancaster before I started taking lessons at Perk Valley. Stuck with me since, and my CFI at Wings for the 172 checkout liked it as well, and said he'd use that with his students.
 
Radial engines are dry sump engines there should be no oil left in the engine case. The scavenge pump should have removed the oil and returned it to the oil tank.

There's the difference for you then: should<>does. The pump would have to run after shut-down to remove the oil.

Think of all the oily surfaces inside the engine at shut-down. All the excess oil drains down and has the opportunity to seep past the rings of the bottom cylinders. Result is hydraulic lock and radial engines have been suseptable since the first one was built.
 
Good to know - I'd swear I'd heard of this with radials, though. Or is it a check that the scavenge pump actually did the job?

There ya go,, we check rather than trust,

Anxiously awaiting the "correct" answer for the pull-through.

The oil passage in the radial is pressure to the crank 2 mains and the master rod, whick sling the oil out t the cylinders, and pressure to the rocker shaft and valve guides. all oil will drain down to the lower cylinder rockerboxes and be scavenged from there to the tank by the scavenge pump portion of the oil pump, which has a check valve built in to hold the oil in the tank and not allow it to drain down and flood the lower cylinder rocker boxes which allows the oil to seep up thru the valve guides and enter the combustion chamber.
 
There's the difference for you then: should<>does. The pump would have to run after shut-down to remove the oil.

Think of all the oily surfaces inside the engine at shut-down. All the excess oil drains down and has the opportunity to seep past the rings of the bottom cylinders. Result is hydraulic lock and radial engines have been suseptable since the first one was built.

All pumps in the radial are mechanical driven and only pump when the engine is operating.

All the oil draining down can't enter the cylinder because the skirt extends about 1 inch into the crankcase the oil will drain down thru the lower cylinder push rod tubes into the lower rocker boxes. where it will be scavenged, and pumped to the tank. and held there by the check valve in the scavenge pump.

Pictures, cylinder skirt, distance the piston and cylinder skirt extends into thecrank case, and the Warner oil pump showing the screen and the check valve inside that cavity.
 

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All pumps in the radial are mechanical driven and only pump when the engine is operating.

All the oil draining down can't enter the cylinder because the skirt extends about 1 inch into the crankcase the oil will drain down thru the lower cylinder push rod tubes into the lower rocker boxes. where it will be scavenged, and pumped to the tank. and held there by the check valve in the scavenge pump.

Pictures, cylinder skirt, distance the piston and cylinder skirt extends into thecrank case, and the Warner oil pump showing the screen and the check valve inside that cavity.

Perhaps you should properly reference your sources. Just to give credit where credit is due. Or were you sandbagging when you wondered about hydraulic lock???

Ok, so there are several paths for the oil to enter the cylinder after shut-down. Perhaps the explanation I was given years ago was lacking in it's totality. The basic fact remains that there is a lot of oil in the crankcase that isn't (and can't be) pumped after shut-down.

As for the check valve in the pump, it's a nice touch but any half-wit designer can build a system that doesn't rely on a mechanical check. Stand pipes aren't just a good idea, they're commonly used in many fluid transfer operations...
 
I thought that was part of the standard preflight. Check fasteners for security and check for excess movement for hinges. Watch the flight control movement while wiggling stuff.

Controls: Don't just wiggle them a little. Move them through the entire range stop to stop. (The Cherokee had some loose wiring after adding new instruments and the flight controls caught on something behind the panel) Check the trim tab for proper operation also. Observing the flight control movement is a given. (I've seen a few people look out the front window while checking free and correct)

Flaps full down. Push up on the trailing edge of the flap and see what happens. Check the control rod attach point. That probably kept me from getting killed in a CE172 one day though it gave the A&P a heart attack. A flap really should not move up 4-5 inches when pushing up on the trailing edge with your hand as you walk under the flap.

After maintenance: Look under the panel for loose stuff. I'll also pull inspection covers off and look inside at pulley's and such. (Our mechanic would leave the covers off for us to snoop in and put on as he walked around the plane with us after an annual. I was stupid back then and wouldn't have thought of that at the time however he insisted we stick our noses and fingers in there and know what stuff is supposed to look like. He also wouldn't give anyone the keys until he flew it himself - good guy)

Pulling stuff off to have a look is not for everyone. If it isn't put back on properly safety is threatened, not improved. As a pilot/instructor/mechanic I can think of any number of pilots that should leave well enough alone. Besides, many items aren't even remotely visible unless the airplane is extensively opened up. Under the floor, for instance, are many cables and pulleys and wires and hydraulic and fuel lines and structural items that you'll never see unless the seats and carpet and floor panels are all torn out.
We regularly see flight controls damaged by aggressive preflighting. Cessna's single-engine control surface skins on everything but the rudder
are structural, corrugated to impart stiffness, and have minimal internal support. Forcing an aileron can buckle or curve those skins, whereupon they act like trim tabs and make the airplane fly wing-heavy. Forcing elevators, especially at the balance weight, loosens the rivets and causes expensive headaches. Forcing the rudder, or just moving it while holding the trailing edge, buckles the skins and can loosen the hinge bracket rivets or even crack the brackets. People seem to think these machines are as sturdy as their cars. Theyr'e not; they're designed to hande strong winds from the right direction, not to take physical abuse.
Canadian law requires an independent inspection after any flight or engine control has been disturbed. A second technician has to look at things like pulleys and safety, turnbuckles and lockwiring, hinges and their pins and/or bolts/and/or cotter pins, check for correct sense of movement and travel limits and so on, and sign a separate entry in the log. This came about after too many backward-aileron hookups and the like and their subsequent crashes, and the rate of those accidents has decreased tremendously.
Looking under the panel after maintenance can be difficult but is a good idea, looking for anything obviously disconnected or fouling the flight controls, but how are you going to see the disconnected encoder plug when it's hidden above a bunch of other stuff? Or the screw waiting to fall between the bus bar and instrument panel? And that's even if you know what you're looking at. Not many people do. And not many are sufficiently flexible or acrobatic to have a look under there with the seats in the airplane. With the seats out it's a pain for me with my stiffening old bod.
There are things you CAN do: Ask your mechanic, politely, if he carries lots of liability insurance. DON'T pressure him into hurrying up the job or you'll almost certainly get something overlooked. DON'T insist that the thing that really needs fixing is "just left alone for now." DON'T cheap out on the job. DO buy him donuts or whatever else he likes to show your appreciation for a job well done; he'll treat your airplane with more respect because you respected him.

Dan
 
Perhaps you should properly reference your sources. Just to give credit where credit is due.

I started to rebuild and work on radials when I was 13 the first was my dad's 330 horse Lyke, and have worked for Firewall forward, Precision airmotive, and the US Navy as engine overhauler doing overhauls and repairs on almost ever make of Radials including the P&W4360

Or were you sandbagging when you wondered about hydraulic lock???

Kinda sorta because I know there are a lot of misinformation and old wives tales about radials.

Ok, so there are several paths for the oil to enter the cylinder after shut-down.

Only 3, the intake valve guide, the exhaust valve guide, and the rings. these are the only 3 places the combustion chamber can get oil
Perhaps the explanation I was given years ago was lacking in it's totality. The basic fact remains that there is a lot of oil in the crankcase that isn't (and can't be) pumped after shut-down.

In fact it is less than a quart in most large radials. I have disassembled 3350s that were shut down on wing for chips lights and found less than a gallon in the tray during clean up. that is the crankcase, accessory case, blower, and PRTs. the little radials that I have set valve clearance on you usually get half of a qt. when pulling the valve covers.

As for the check valve in the pump, it's a nice touch but any half-wit designer can build a system that doesn't rely on a mechanical check. Stand pipes aren't just a good idea, they're commonly used in many fluid transfer operations...

For starters, every radial engine installation I have worked on returns the oil to the top of the tank, to a de-airation plate, the check valve retains only the oil in the return line.

Any oil getting into the cylinder must first seep thru the oil control ring which has holes behind it to allow the oil to drain into the piston, it must first fill the bottom cavity of the piston befor it can get to the compression rings and combustion chamber.

Most every hydraulic lock in a lower cylinder of the Radials is caused by a bad oil pump, having worn gears in the pressure side of the pump, which allows the oil from the bottom of the oil tank to seep around the pump gears and into the crankcase of the engine. and then drain down the pushrod tubes and flood the rocker boxes, and enter the combustion chamber thru a worn valve guide and open valve.

The big plume of smoke on start up is from the oil in the exhaust stack burning off. not from oil being burned in the combustion chamber.

The most dangerious thing that happens is the oil will fill the intake tubes of a lower cylinder with a closed intake valve. then the next intake stroke the oil is pulled into the cylinder with the engine cranking or fireing a upper cylinder. That gets expensive because the rod in that cylinder will get bent, and draw the piston into the path of the crankshaft counter weights. and the engine will destroy its self.

see the pictures
 

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So you are a sandbagger. Too bad.

The slightly worse side of it is when you repeatedly claimed the crankcase should be dry after shut-down. That obviously isn't possible.

You could have remained honest even when replying to my correct note that oil and gravity caused hydraulic lock. In fact a simple discussion of the possible paths would have been appropriate.

I trust you know where you stand in my book...
 
So you are a sandbagger. Too bad.

The slightly worse side of it is when you repeatedly claimed the crankcase should be dry after shut-down. That obviously isn't possible.

You could have remained honest even when replying to my correct note that oil and gravity caused hydraulic lock. In fact a simple discussion of the possible paths would have been appropriate.

I trust you know where you stand in my book...


And for a guy with so few posts here, when you jump on Tom like this for trying to help us learn a little about aviation, you will undoubtedly be in the same place in a lot of books.
I have worked on dozens of Porsche 911 dry sump engines and the scavenge pumps don't leave much oil in the bottom end after shutdown. If the pump is trash or the check valve is bad it will drain the oil into the sump overnight (almost all of the 10 quarts) but fortunately for the owner of the 911, it just fires up and the pump puts it all right back into the tank.
If you have credible knowledge that refutes Tom's statements here, please post away. But to call names and call someone dishonest without refuting the statements you question with your own version of just how and why the statements are incorrect is just a cheap shot. Any moron would know that oil and gravity are the root cause just as any moron would tell you that the sun is the root cause of sunburn.
 
And for a guy with so few posts here, when you jump on Tom like this for trying to help us learn a little about aviation, you will undoubtedly be in the same place in a lot of books.
I have worked on dozens of Porsche 911 dry sump engines and the scavenge pumps don't leave much oil in the bottom end after shutdown. If the pump is trash or the check valve is bad it will drain the oil into the sump overnight (almost all of the 10 quarts) but fortunately for the owner of the 911, it just fires up and the pump puts it all right back into the tank.
If you have credible knowledge that refutes Tom's statements here, please post away. But to call names and call someone dishonest without refuting the statements you question with your own version of just how and why the statements are incorrect is just a cheap shot. Any moron would know that oil and gravity are the root cause just as any moron would tell you that the sun is the root cause of sunburn.
Click on Clark's name, then "Find all posts" and peruse. This is not unique for him.
 
There's the difference for you then: should<>does. The pump would have to run after shut-down to remove the oil.

Think of all the oily surfaces inside the engine at shut-down. All the excess oil drains down and has the opportunity to seep past the rings of the bottom cylinders. Result is hydraulic lock and radial engines have been suseptable since the first one was built.


Nope, not enough oil in the engine at any given time. Most of it is in the cooler and tank.
 
I'm STILL waiting to know why you pull a radial engine through, if not for hydraulic lock.

Tom was trying to point out that the hydraulic lock check was the secondary result of checking the oil pump and check valve which are actually more critical than the hydraulic lock. The hydraulic lock will only screw you on the ground, but clearing it will not get you out of the woods, because the reason it happened is because you have an oil pump issue which is going to quickly turn into an inflight catastrophic failure which is worse than ground/start catastrophic failure.

Now, can you guess why I would pull through 12 blades on a radial I operated?
 
So, I haven't seen anyone mention trim tab actuators and their play. That's one that can kill you pretty easy if it's on the elevator.
 
Click on Clark's name, then "Find all posts" and peruse. This is not unique for him.

Yup, it's not unique for me. I call'em like I see them. If you don't like it then don't read my posts. Pretty simple hunh?
 
And for a guy with so few posts here, when you jump on Tom like this for trying to help us learn a little about aviation, you will undoubtedly be in the same place in a lot of books.

Note that I didn't question the knowledge, I dismissed the method of conveying the information. Can you understand the difference?

The poster feigned ignorance along with making misleading statements and then claimed authority. Maybe that's an acceptable teaching method in your world buy it doesn't work in mine.

In other words, he gave a gift of knowledge and I returned the favor. Maybe the poster will learn to be honest in their teaching method, maybe they won't. At least I gave them the opportunity to learn.
 
Nope, not enough oil in the engine at any given time. Most of it is in the cooler and tank.

So how much oil in a cylinder does it take to lock an engine?
 
So, I haven't seen anyone mention trim tab actuators and their play. That's one that can kill you pretty easy if it's on the elevator.

PArt of Cessna's inspection program is a tab free-play check. It's not usually any issue. The Grumman singles, on the other hand, have that stabilator tab that has a little bellcrank riveted to it, and I've seen that bellcrank flopping around loose, ready to fall off. Now THAT'S a hazard.

Dan
 
Wow, I must be going color blind. I THOUGHT this was the blue board, but it's starting to look red to me.
 
Wow, I must be going color blind. I THOUGHT this was the blue board, but it's starting to look red to me.

Its because we no longer have a reputation system to control such garbage.
 
Yup, he's the ONLY person on this board I've ever put on ignore...


Now don't be too hard on ol Clark, he's just trying to cope with finding out what he has believed all his life is wrong.

but that is another thread creep.
 
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