Prop Safety

[Rusty]

Hello Guys,

After reading the prop failure thread and Air Ministries' comments on checking props, I felt maybe we should discuss prop safety. 

I have not had many prop failures in my 62 years of flying models.  I had props props come off because I didn't tighten the prop nut enough or check it periodically. 

The topic is important to me because I do have over 300 props dating back to Ritz, O&R, Top Flite white nylon, etc.  I have APC that I notice are changing color.   

What I know about props is to balance them.  I heard of people putting old nylon props in boiling water.  I never did it.

What are the rules and tests to see if any props in my collection are unsafe?  I know if they have cracks, knicks, etc, that shows to discard them.

Rusty

[Doug Moisuk]

Propellers are notorious for inflicting serious bodily harm while vigorously defending their space" George Aldrich

[Mike Griffin]

Hello Guys,

After reading the prop failure thread and Air Ministries' comments on checking props, I felt maybe we should discuss prop safety. 

I have not had many prop failures in my 62 years of flying models.  I had props props come off because I didn't tighten the prop nut enough or check it periodically. 

The topic is important to me because I do have over 300 props dating back to Ritz, O&R, Top Flite white nylon, etc.  I have APC that I notice are changing color.   

What I know about props is to balance them.  I heard of people putting old nylon props in boiling water.  I never did it.

What are the rules and tests to see if any props in my collection are unsafe?  I know if they have cracks, knicks, etc, that shows to discard them.

Rusty

Rusty, I agree with your concern and the premise of this post as I have been a victim of bodily damage from props although it was my carelessness and lack of attention, not from a faulty prop.  The thread I started about my friends prop that just flew apart, was something I had never heard of before and I dont think there was anything that could have prevented that type of structural failure. 

Maybe we should start examining the prop more closely before mounting it on the motor, especially if it is a wooden prop. 

Mike

[Steve Helmick]

I'm a fan of prop safety, for sure. I saw a club member flip the yellow Tornado nylon prop on his McCoy redhead sport engine. The prop was old, but apparently in good shape until he tried to start the engine with his finger and one blade just fell off. Nothing hurt, because the engine did not start. I used a lot of Tornado nylon props in years past, without a problem, so I think age was the problem. Some will chip in that boiling the props in water will make them safe, but I don't want to take that risk, do you?

The closest I can recall happening to me was trying to bench test an early K&B .40 FI I'd modified for a FF friend. I looked up the PGF Chinn engine review and bought one of the props that was used on the test, a 9-6 TF Super M, as I recall. The grain looked a bit sketchy, but it was the only one the LHS had. The tip came off when I flipped the prop, but again, the engine didn't start, so it was pretty harmless. I did manage to hand start it with a wooden TF "Speed Prop", probably an 8-8, and it really howled on that and 40% vitamin N. I was a bit amazed that it'd start on such a light, thin, and narrow bladed prop.

I don't recall any thrown blades when I flew speed models, either mine or others, except when a model grazed the ground and took off both blades by brute force. Exciting, but not really hazardous. But when I first started flying CL with the group of teens over in Pullman, WA, one of the guys had previously thrown a blade off the TF nylon 10-6 on his McCoy .36 "Super Stunt"/Berkley Grumman Guardian. Ripped the engine right off the plane and sent it flying. Unfortunately, they were flying inside the college "Field House", and impacting the masonry wall destroyed the engine. Yes, some danger in that instance. TF sent him a new prop, so we were not fans of TF nylon props, despite the reports of the 10-6 TF nylon winning the '58 NATS. 

I'm pretty impressed with APC. Not only do they work very well, their website has a page devoted to maximum safe rpms for their props. Can't think of anybody else with that much foresight. Very smart, IMO.    Steve   

[M Spencer]

https://www.ulprospector.com/knowledge/1489/pe-dry-vs-conditioned-polyamide-nylon/

 " I heard of people putting old nylon props in boiling water.  I never did it. "

According to something o Barton , 80 degrees F  for 20 or 40 minutes.

A lot of 60s prop instructions WERE top Boil Them before  use .



IF you get a dash pad thats sat in the sun  for tyen years , unmoved , spray a wet coat on in the afternoon , another when its ' gone ' , anopther next morning ,
and another three , it'll be as flexable as new in a week . Whereas it woulda cracked if you spat on it , as it were . Dropped anything on it , anyway .
If it IS a dash pad , repair split / crack BEFORE you go at it withit .
THE POINT being , if you try the same on your old Nylon Props a wseek before you try and pull the blades off , youll be fine . Or doing your best , anyway .

Mr Towells prop bag is Flannel , say 20 x 30 inch , Folded over for twelve inch od , with 2 in pocket witdth . od. or 1 3/4  or half , so you can get your fingertips in to grab the prop tip
The losse to 6 inchh folds over , then its rolled . But still , mowers , toolboxes , jacks and thngs can whack into it when you land after getting airbourne , or similar .
So it wants to go on top or in a pocket . Or wood box . With a catch on the lid .
When you think of what youve paid for decent props , a storage travling doodad is well justified . Whipped up by Her Indoors , no doubt . Soft Leather would do well too .



Along these lines , One Row of pockets , say a inch deeper than your longer props , With the top folding over so they dont go awol . The straps rather needed , also .

[M Spencer]

https://www.aviationsafetymagazine.com/systems_check/preflighting-propellers/

headaches : https://reports.aerade.cranfield.ac.uk/handle/1826.2/11

https://www.aopa.org/training-and-safety/online-learning/safety-spotlights/aircraft-systems/propeller-safety

and last but not least ;

https://www.aircraftsystemstech.com/p/propellerinspection-and-maintenance.html



Take Two Steps Back from the prop , before pracing about and trying to getat the needle . . Best to ' come around clear ' of the plane . Before coming in at the needle .So stumbles dont lead to tears . Distracting annoying blathermouths should be removed before start up . A brief run ' through the proceedure ' ( dry run / practise ) for uninitiated  crewmen .

If you imagine your elbows out and a weight in each hand , during it , anything that'd get clouted should , and kicked in the ass , before ' switches ON ' .

The SAME RULES apply !



SO , as most people inna club , know : A dry motor , essentially , a measured prime . Swing it thru Fwd. say ten times . The Reverse / Backward , to clear the prime .
IF its been stored and oiled , a generous prime , as above , pull the plug & flussh the oil outta it . Belt the engine over 10 ntimes to clear the fuel n oil .
Check yer plug / ammeter . Reinstall , Fuel .
Maybe check for ' bump ' Switches 'ON' .

BUT , fuel up - to the intake . SITE CLEAR of morons . ( visual ) Circle CLEAR .  Observes well clear . Put down the brick .
SEE the elppers olding it .Eye Contact or suchlike . Nod , or talkitive types - exchange words .

Swing Prop FWD.  up against compression - with the blade level - horizontal ( so it wont catch it if it Stops inverted .)
Swith ' ON '  verbaL .
Nod at observers , pit man , and others wIth dIrect  relevance .Nonchalantly belt the inboard prop blade DOWN . So it swings past a alf turn , up against compression -
The kick back will belt  it harder over compression the krekt rotation , so it will start itself . Asa the motors damp & free , and the Plugs HOT . fuel spark air , is whats needed.
And STAND CLEAR after yertwo steps back . Walk Past CLEAR . As were not all 1000% all of the time . A DRILL or PROCEEDURE adheared to to place bits away from dangerous bits. and ties , glasses  , pens in pockets , and anything else loose , outa da way , like swinging the field box / glow start - clear . pre planned and adheared to . Step by Step ,

displays airmanship of a professional standard . So we dont get amaturish incidents . So irdiots Yelling except say a Clear ' HALT ' if say someone else has thrown a brick your way
are liable to throw things into the works . So Start Up is no time for idle spectator chatter . Like a Rider on the Grid . Pick a better time for it .

Airmanship is skill and knowledge applied to aerial navigation, similar to seamanship in maritime navigation. Airmanship covers a broad range of desirable behaviors and abilities in an aviator. It is not simply a measure of skill or technique, but also a measure of a pilot’s awareness of the aircraft, the environment in which it operates, and of their own capabilities.[1]

Situational Awareness . On a Motorcycle , Ten Fold . No less desirable . Air Heads Not desired ! particularrly pillion .;

[Rusty]

Propellers are notorious for inflicting serious bodily harm while vigorously defending their space" George Aldrich

What a true statement.  I was cut severely at age 12 because neither my Dad or I knew how to safely handle a Voodoo.  The failure came because he held the model from behind and I started the KB Stallion 35.  He told me to hold the model from the front while he adjusted the needle valve.   When I went to put my hands on the wing, my thumb went into the prop arc and it cut the tip of my thumb and when I jerked my hand the base of my thumb went in the arc.  I had to get stitches on both cuts.  Luckily, it didn't cut the tendons.   I look back and wonder how could have been so stupid. 

My first experience with others getting cut was in about 1970, age 15 when we was flying RC.  I was flying a Goldberg Skylark and I heard a guy scream, I got my finger cut off.   I look down and was shocked and NEARLY let my plane fly away.  My Dad yelled at me, turn back, turn back.   I had trouble even spotting the plane.  The guy stuck his hand in a VECO 61.

A while ago a guy I know was running a Saito 91 on the bench.  He tried to adjust the needle from on front of the engine and stuck his hand in the prop arc, WIDE OPEN. It cut 3 fingers off with the skin holding the pieces on.  He wrapped his hand up and drove to the ER.  While in the ER he went into cardiac arrest and had to be resuscitated.  They was able to reattach some fingers. 

Recently, a guy in the club had his index finger cut off by an electric motor.  They didn't reattach it. 

[Rusty]

Rusty, I agree with your concern and the premise of this post as I have been a victim of bodily damage from props although it was my carelessness and lack of attention, not from a faulty prop.  The thread I started about my friends prop that just flew apart, was something I had never heard of before and I dont think there was anything that could have prevented that type of structural failure. 

Maybe we should start examining the prop more closely before mounting it on the motor, especially if it is a wooden prop. 

Mike

Mike, that is why I started the thread, to get others to explain how they inspect and make sure their props are safe.

Thanks

[GallopingGhostler]

I believe that the boiling process for preservation was when the props were new, not after they have aged and have developed "microscopic" cracks. I'd never trust NOS nylon props.

But I must admit, back in the 1970's, they were the least expensive, and properly balanced for sport use, (otherwise notoriously out-of-balance - Top Flite white plastic silkscreened trim red) did me a lot of good on my Cox reed valve powered half-A planes. I have no experience with them on larger engines (except the 1965 model OS Max .10R/C, but still a small engine).

Yes, without proper hand protection and care (and yes, I've had my share of potential Darwin awards), they can really bite nasty.

[Paul Taylor]

I have boiled nylon/ glass props to dye them in the past.

Also another good reason for electrics is your not flipping a prop or really a need to tach it.
But I did have a prop rub a 1/6 in notch on a flight on a APC prop. No real damage to the plane. I did not want to chance it so I swapped it.

[Motorman]

Can we all just make a gentlemens agreement right now to go out in the shop and throw out all our Tornado props.

[Dave Hull]

You can throw them out, or you can wait for them to self-destruct. One sets you back a couple of bucks, the other has unknown and unbounded costs....

This was a 3-blade--before it became a hub and three "epoxy spreaders" scattered across the circle.

[GERALD WIMMER]

Hello Worst finger chopping accident I have had was using an electric starter, where my thumb on the hand holding the model slid forward and went into the prop arc. Lots of shed blades over the years normally nylon Top Flite or Tornado but even Cox 049 will too. Normally they are too old and gone hard. Never had problems with 'new' Tornado soft white nylon props or the new Australian Taipan props we use for combat.

Regards Gerald

https://www.wightsmodelaircraft.com.au/taipan-propellers/

[Paul Smith]

This have more to do with the RPM of modern engines than prop strength.

Old wood and plastic props are generally OK on old engines.

We used to throw a blade now and again on FAI Combat planes that went fast and turned quick due to gyroscopic precession. 
The first time I replaced a Fox Mark VI with a Nelson 36, using the same plane, fuel and PROP, it threw both blades on the first hard fast turn.

[Dave_Trible]

This have more to do with the RPM of modern engines than prop strength.

Old wood and plastic props are generally OK on old engines.

We used to throw a blade now and again on FAI Combat planes that went fast and turned quick due to gyroscopic precession. 
The first time I replaced a Fox Mark VI with a Nelson 36, using the same plane, fuel and PROP, it threw both blades on the first hard fast turn.

I'm betting this is closer to true about these old generation props.  I've had one 'plastic' prop chuck the blades.  That was just a few years ago an old Wasp .049 threw the blades on a prop I couldn't identify but was made with a strange opaque white plastic-looked like pvc.  I have a couple props that came with the Russian Raduga 7 engines that look like the same stuff-I won't use them.  Other than that I will run the old white nylon or grey Grish three blades on OLD style engines with normal precautions to let the prop have it's space and stay out of the prop arc as much as possible.  I have boiled a few in case the nylon has gotten brittle though I don't know if it really makes a difference-maybe does.  I used nylon props back when in combat because you could usually hit the dirt with them and do nothing but bend the blades back a little .  You could restart and get back in the air without loosing air time over changing a prop.  Hard to think a forever plastic could deteriorate that much but I wouldn't trust a BRAND NEW one on a modern high output engine except the glass filled APCs.  I've turned those all day over 10,000 rpm without failure.

Dave

[GallopingGhostler]

I'm betting this is closer to true about these old generation props. [...] Other than that I will run the old white nylon or grey Grish three blades on OLD style engines with normal precautions to let the prop have it's space and stay out of the prop arc as much as possible.  I have boiled a few in case the nylon has gotten brittle though I don't know if it really makes a difference-maybe does. I used nylon props back when in combat because you could usually hit the dirt with them and do nothing but bend the blades back a little .  You could restart and get back in the air without loosing air time over changing a prop.  Hard to think a forever plastic could deteriorate that much but I wouldn't trust a BRAND NEW one on a modern high output engine except the glass filled APCs.  I've turned those all day over 10,000 rpm without failure.

Dave, I think you are on to something.

If interested, one can read up on various engines: legacy cross scavenge, more modern Schneurle, and somewhere between (i.e., Perry Directional Porting - PDP), examine their horsepower and torque curves under varius fuel mixes and RPM's with various props.

https://sceptreflight.com/Model%20Engine%20Tests/Index.html

The older sport and stunt engines peaked out at lower RPM's, thus one would go to larger diameter or steeper pitched props to provide the needed thrust. In stunt engines, we tend to run them in control line running a rich 4 cycle breaking into a faster 2 cycle in stunts, or a wet 2 cycle breaking into a faster solid 2 cycle in stunts.

A few years ago, I was amazed that by substituting a legacy Enya .15-III TV with throttle locked wide open turning a Masters 8x6 could do the same lap speeds as my OS Max .15FP-S turning a Masters 8x4 prop. Plus, the engine could do a clean wet-2 to clean-2 in stunts then return to a wet-2. According to Peter Chinn's test on Sceptre Flight's Sept. 1967 Model Airplane News article, on 5% nitro it peaked at 13,700 RPM (typo in writing - going by test curve). Yet the OS .15-LA Schneurle peaks at 17,000 RPM, several thousand RPM higher. The venerable Fox .35 Stunt peaked at 12,000 RPM, but in stunt runs, it and other comparable legacy engines of the era in practice, run at lower RPM's than that.

That IMO went ditto with the smaller higher RPM Cox half-A reed valve engines, which are also torquers. I learned early on in my single channel rudder only R/C days, that I got the same flight speeds on my Cox .020 Pee Wee turning a nylon T/F 5.25x3 prop as the Cox competition 4.5x2, but I got 1 minute longer engine runs due to the lowered RPM's. Plus, the T/F nylons were cheaper ($0.35 at the military base stores versus over $1 for the Cox gray props) and they didn't break when striking the grass like the Cox props. If a tip chipped, I'd simply trim both prop tips off and rebalance, continue to use.

The older engines provided similar power at lower RPM's. In the latter 1970's, the late William "Bill" Winter decried the fact that manufacturers had given up on the older cross scavenge engines for Schneurle. He pointed out that they should have continued to sell the older engines, emphasizing that they are "torque engines".

I am not particularly worried about us older generation, because we through experience (and paddlings - a no-no  these days) know how to do risk assessments. Today, everything is fraught with warnings and all sorts of safety devices we lived without (since lawyers got involved: problem, reaction, solution), because then, we learned responsibility as children, taking on such at an earlier age. (The acadademically better kids in 5th and 6th grade did JPO (Junior Police Officer) duties holding stop signs to stop traffic and escorting children across the street with a teacher supervising. Nowadays, only volunteer parents are permitted to do this, depriving the kids of learning responsibility at an early age.)

Heck, I remember as an adolescent in Biloxi, Mississippi, being able to buy cherry bombs, M-80's, and larger than bottle rockets from fireworks stands when I turned 12. Younger, I rode my bike all over the place without parental supervision.

Nowadays, even teens must have parental supervision.

Why did we survive? As Brad Upton put it, "We used to play with guns, knives and fireworks when we grew up. There were no dumb kids, because they didn't make it!"