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Author Topic: Icing on the props  (Read 557 times)

schrambow

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Icing on the props
« on: January 21, 2020, 08:50:58 pm »
Hello,
my endless series of questions for the folks on here.

My last flordia trip at FL25, encountered some light rime icing and turned all the deicing equipment on.  Engine inlet heat on and igniters came on as well.  I didn't really get excited much since it was light rime and really wasn't collecting fast at all.  Plus, i thought in about 5 minutes or so, i would be out of it (not sure why, i guess i was over Georgia and its warm in Georgia, lol).  Well after about 10 minutes i was still in it and there was about an 1/8 inch of ice on the leading edge so i cycled the boots on one cycle.  Another 5 minutes goes by and I am still in this light icing and all of a sudden the left engine started an imbalance and a slight vibration.  I recognized this imbalance right away, as in the past our 681 experienced this once when we were in moderate icing and had one blade heat failure and it setup the same type of feeling i was experiencing here (the other 2 blades in that 681 were working fine we found out on the ground).  So i immediately requested a climb to FL27 and i was out of the icing at about FL26.  I flew for about 8 minutes out of the icing at FL27 but the imbalance was still there and not going away. So i thought i better head down hill to warmer air and get this imbalance gone.  At about FL17 the imbalance was gone and so i went back up to FL20 the rest of the way problem free-sort of i still have a small comm issue).
Got on the ground and all blades both inboard and outboard of the prop heat are working great, so i couldn't find any failure?
Have any of you ever had any experience like this before in your turbines?
Couple of other things i may should or could have done.
1.) Turned off the prop sync perhaps?  Although i didn't think it was doing anything abnormal to either engine?
2.) I was was  97 percent cruise, i thought of quickly bringing the conditioning levers up to 100% and them back down to 96%, but wasn't sure this would do anything that was sticking on that prop, plus i didn't want to abuse this turbine engine?  Piston planes we used to cycle the props in moderate icing and it would help out quite a bit to shed ice.

Inspecting these props again tonight, They were overhauled and new prop heat's were installed last winter, however, these props were sand blasted a year ago at Peoria runways last winter when it was 20 below zero and they sanded those runways back then. In my training, i did two heavy beta stops back then on those runways and the new looking propellers have sand blasting on them. The only thing i am thinking now is to polish these prop boots up real nice with some PBS and get them so one would need sunglasses to look at them directly? 
Do any of you know what the best material would be to polish these babies up so ice can't bridge or build up on them- anything better than Pbs?  Any experiences with prop imbalances from anyone?  Can't be good for the engines i would imagine operating them for a longer time period of imbalance i would guess?



donv

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Re: Icing on the props
« Reply #1 on: January 21, 2020, 11:31:34 pm »
I have definitely had that imbalance thing happen in icing. Not that uncommon, really.

I typically cycle the props up to 100% or so and back down, and that often takes care of it.

Have you had ice come off the props and hit the fuselage yet? That's always fun. I'm not looking forward to that on my new paint, but it will happen sooner or later.

While we're talking about icing, were you running the ignition?

donv

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Re: Icing on the props
« Reply #2 on: January 21, 2020, 11:46:32 pm »
In fact, in the 980 AFM in the Normal Procedures, Flight In Icing Conditions section, it specifically says the following:

"Relieve propeller imbalance due to ice accumulation by increasing and decreasing RPM. Repeat as necessary."

I really appreciate questions like this, as it causes me to review these things also!

schrambow

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Re: Icing on the props
« Reply #3 on: January 22, 2020, 09:56:24 am »
good to know Don about AFM, thanks for sharing.
What about any material (PBS) to use on the prop deicer's? Any special sauce to use that will get it really slick also to help shed ice?

https://www.aircraftspruce.com/catalog/cspages/pbsbootsealant.php

this is the stuff i am using, but not sure it is the best for making it really slick?



Adam Frisch

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Re: Icing on the props
« Reply #4 on: January 22, 2020, 11:07:24 am »
On the 680V the igniter switch is spring-loaded. No way to keep them on full time, even though I had igniter boxes exchanged to the continuous type. I'm thinking that by accident some day, someone, somewhere, unbeknownst to me, broke into hangar, removed the spring in those switches, put every thing back together again and left it like that.... ;)
Slumming it in the turboprop world - so you don't have to.

donv

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Re: Icing on the props
« Reply #5 on: January 22, 2020, 12:20:12 pm »
One of the best things I have done recently is to scan my AFM, so I always have it available on my computer. It makes looking things up or just refreshing my memory so much easier.

schrambow

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Re: Icing on the props
« Reply #6 on: January 22, 2020, 03:30:21 pm »
Taking this thread sideways and getting away from slippery props,
if you have a scanned PDF of the AFM on your ipad in the cockpit, do you then need to carry the 10lbs written flight manual?  Could bring 2 more gallons of fuel if the PDF on the ipad would suffice the FAA?

donv

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Re: Icing on the props
« Reply #7 on: January 22, 2020, 06:39:48 pm »
It might work, but I don't really see the benefit so I always carry my proper AFM.

schrambow

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Re: Icing on the props
« Reply #8 on: January 23, 2020, 04:16:55 pm »
Went to the hangar today to spiff up the prop boots.  Put 4 coats of PBS on them today and have them nice and slippery looking now.  The problem is, with the props looking all beautiful now, the rest of the wind and tail boots could use a few coats of this stuff too as they are dull looking now compared to the props. More elbow grease to be done i guess now. ::) 

Steve binnette

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Re: Icing on the props
« Reply #9 on: January 23, 2020, 06:40:15 pm »
I really like to use ICEX.  It is made for your boots but I also apply it to the entire prop blade.

It only last a couple of flights so I only apply it when I expect icing.   

In addition to PBS, Goodrich also make a treatment for you boots.  These are more of a cosmetic application but I have to believe they aid in shedding ice.
« Last Edit: January 23, 2020, 06:46:34 pm by Steve binnette »

schrambow

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Re: Icing on the props
« Reply #10 on: January 23, 2020, 10:23:56 pm »
Sorry about being a little obsessed about this subject. 
But looking at your props Don, you have the q-tips i see, and your prop boots seem to be about half the length of our prop boots that we have on the Dowty's?  I for some reason never really paid that much attention to the different length of prop boots compared to the different props that are on our Jetprops? 
Prop boots are specific dimensions for each type of different prop i am assuming now or what determines their lengths?  Q-tips, widecords, dowty's, etc... i wonder if some handle ice better than others now?  I assume there wouldn't be any scientific data on this but just personal experience from those whom fly all of them? 
Sorry, but i find this kind of interesting though.

Bruce Byerly

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Re: Icing on the props
« Reply #11 on: January 23, 2020, 11:24:03 pm »
The Dowtys originally came with a shorter boot. Then I believe there was a bulletin to put some tape on the leading edge to help shed ice evenly, then the long boots became standard.  Someone probably remembers how and when the changes occurred better than me, but the long boot was an evolution.

I think the icex or similar is a great idea.  Regardless of brand, imbalance due to uneven shedding is definitely not uncommon and flexing the props and AOA via cycling rpm helps.  Those days in the Great Lakes Ice machine with the props slinging the ice onto the fuse ... oh what fun!


donv

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Re: Icing on the props
« Reply #12 on: January 23, 2020, 11:49:04 pm »
My props are the wide chords, and yes, the boots are shorter than on the Dowtys. Seem to work just fine though, and now that I think about it, I think the uneven accumulation might be a little bit less on the wide chords. Bruce would know.