By KEVIN GARRISON
We never talk. Why is that? I sometimes think you take me for granted, but you need to know that I am a driving force and the first thing air hits when it deals with your airplane.
Here are a few things about me that you need to know.
Consider me an airfoil, not a paddle
It is easy to think of me as a sort of “oar of the air,” but I have all the characteristics and behavior of any other airfoil.
Propellers have an angle of attack, just like your wing, and also like your wing, your propeller can stall. I utilize Bernoulli’s principle and Newton’s third law, and I operate best at my optimum angle of attack (minimum lift to drag ratio) just like any other airfoil.
Please don’t push me
Or pull me, for that matter. Props are not handles and should not be used to push your airplane into and out of the hangar.
Please use a tow bar or consult your aircraft’s Pilot’s Operating Handbook (POH) to find designated push/pull points on the airframe.
Handling propellers this way can cause them to bend slightly out of whack, and it can mess up the hub seals.
Make me part of your preflight
Look carefully for surface damage and irregularities, such as dents, nicks, scratches, and erosion. If you have any doubt about my condition after finding something, please have a mechanic look at me. They can correct minor damage by “dressing” it out.
Check my spinner just as carefully and please make sure you check the back surfaces of my hub — this is where cracks are most likely to occur.
Don’t hose me
Never use a water hose to clean me. I prefer an oily rag for my hygiene, thank you very much.
A rubdown with an oily rag is the best way to clean me during your preflight. The oil removes substances that cause corrosion and helps me repel corrosives and water erosion during my next flight.
Water, especially water squirted into my spinner and hub, can lead to corrosion and lubricant breakdown — and nobody wants that.
Clean me every 100 hours with a non-petroleum solvent and waxed just like the family car, using paste wax.
Treat me like a loaded gun
Assume that my mags are hot and ready to fire at all times, even when you know for sure that there is no way for my engine to start.
You cannot be too safe around me and a little extra care will help you keep your fingers and hands.
Rev me gently
High-power, static run-ups over gravel or dirt can lead to all sorts of FOD (foreign object damage). High-speed operation of your propeller around loose gravel or dirt can cause me to get nicks and other damage.
If you find yourself taking off from gravel or dirt runways and you can safely perform a takeoff this way, keep the power back from maximum takeoff settings until you get some decent airspeed heading down the runway.
And please scrutinize me carefully after operating on gravel and dirt.
Don’t worry if I wobble
My tips might wriggle just a little if you move them by hand. Tiny differences at my blade roots become magnified many times when measured at the tips.
This slight wobble does not affect my performance or safety at all. After the first turn, when the engine starts spinning me, centrifugal force sets my blades firmly into my retention bearings, and all is well.
Chronicle my life story
My history needs to be in a separate diary and my maintenance is vital. Records of my history, maintenance, and service bulletins are just as crucial as your engine and airframe maintenance logs. It is an excellent idea to maintain a separate record of propeller issues and maintenance.
Most people don’t talk about propeller overhauls, but my efficiency and safety are just as important as the engine’s or wings. My overhaul interval is generally based on service hours, but can also be predicated on calendar limits.
Apparent damage and wear can also make my date with the overhaul shop come sooner.
If you are buying an aircraft, your pre-buy inspection done by a mechanic should include a careful review of records and inspection of the propeller. A bent or damaged prop might indicate current or future damage to the engine.
I could run away
A runaway occurs when my propeller governor fails during flight. When this happens, I am designed to default into a flat pitch setting. This can cause me to speed up and cause the engine to over speed.
The standard recovery for this is to pull your engine’s power back and raise your nose to get things to slow down. I rarely do this, but you should know the procedure to follow in your aircraft should this happen.
“Beta” is not the name of Captain Kirk’s creepy girlfriend
It is a range and a setting. Beta control is the repositioning of the propeller blade beyond the normal low pitch stop. This is also sometimes referred to as a “flat pitch.”
Most aircraft with beta control and prop reversing very rarely, if ever, actually go into reverse thrust. Beta range is more than enough to make almost any aircraft stop on a dime.
“Flicker Vertigo” is not just a cool name for a band
This can happen to a pilot when sunlight reflects into the cockpit in just the right way off of the back side of my rotating blades when the sun is behind me. This is why my backside is finished in a non-reflective flat black.
I am also painted on the front side with bright colors near my tips to warn ramp dwellers and aircraft service people not to walk into me.
Thanks for listening. I’ll see you next time you come out to the airport.
Enjoyed the “first person” comments by the propeller!
Nice piece and always a good primer. I think we over use the absolutes when we talk about pushing or pulling an aircraft. Most acft that have a CS prop also have “real” tow bar attach points that can actually be used to push and pull and are heavy enough to use tow equipment so it’s appropriate to not work the bearings or seals on that bird. An acft with a fixed pitch prop often has lousy, single handed tow points. There using the HUB area may be a “best option”….
I have been known to (gently…) head smack grown adults (I’m 6’2” and 75 years old) for leaning/resting on/THINKING about putting ANY pressure… on the spinner…after a first warning..).
“We” might also introduce the correct terminology where the “face” of the prop is the more flat surface, the side the pilot is facing, and the (humpy) back is the arched part of the airfoil… (sorry.. the old A&PIA instructor and cfi kicked in like the old English teacher but without the red pencil…🙄). And the bits about fixed pitched props and overhauls…you bet!…your life….
I had to do some Googling after I read, “wipe with an oily rag”, and, later, “clean..with a non-petroleum solvent”.
I am guessing Turpentine and Naptha are what you are getting at?
I’ve never understood why pulling on the prop should be avoided. A lot mote force is exerted when flying
If you must, push or pull at the hub only. A pilot organization where I used to live had a C-150 that the students and pilots used to use the prop to push and pull it around. On a student training flight, one prop blade failed with the outboard section departing. That threw the engine so far out of balance that it came off it’s mounts breaking the mixture cable and mag leads in the process, so that out of balance engine couldn’t be shut down. The cowling is the only thing that kept the engine on the plane so the CG was still compatible with flight allowing for an emergency landing on a dry river bed. That’s why, as a rule, you don’t push and pull on the prop. Realistically, you won’t hurt a fixed pitch prop pushing or pulling near the hub, but one should never pull on a prop far enough out to cause the prop blade to flex.
It is generally due to asymmetric load on the prop. and crank,the crank flange is actually fairly weak. The danger to the propeller on a fixed pitch is the chance of bending a blade if the force is NOT kept right by the hub. With an adjustable/constant speed unit the hub seals can be damaged. During operation adjustable prop. blades are flung outward with unbelievable force that is far grater than the thrust force pulling forward on the blades.
I have a short story on the fixed pitch prop on our 1961 Cessna 175B. It has 4,000+ hours total time and the logs show that the prop was never off the Engine.
Last annual we decided to send the prop for overhaul, since it was way over the 7 years and 1,500 hours that McCauley recommends.
Stockton Prop was doing final cleaning when they found a crack in the center bore, inline with a bolt hole….obviously ‘red tagged’.
We were a short time until the prop may have failed…..!
We now have a newly overhauled prop and we’ll be pulling it off in 7 years and sending it to overhaul.
So, fixed pitch props can fail. Ours had 10 **9 th cycles, off the cycles life charts.!