RB211 spinners

[RUDAS]

I heard from someone who's been in aviation much longer than me that the rb211 engine's spinner is desiged in a sharp conical form to prevent ice-buildup,and that if icing occurs,the conical shape will lead to an imbalance and the ice will therefore 'spin'loose and be fed back into the engine.

Sounded a bit odd to me.

Anyone with technical/design knowledge know if this is true?

[gas path]

The Spinner is indeed conical and pointed but the tip is made from a hard rubber compound, if ice should start to form it would cause an imbalance, the tip would start to 'wobble' and shed the deposit before it got too big. Works well from the D4 to the current Trent.
BTW no rubber tip....no dispatch.

[RUDAS]

thanks for confirming what i was told.i thought it was a bit odd to intentionally shed the ice back into the engine though,although it might not be very big at that stage,is it not possible that the ice might cause blade damage?

[gas path]

Rudas
The idea of the rubber tip is to prevent any ice buildup getting big enough to cause a problem in the first place.

[747FOCAL]

RUDAS,

Those engines can swallow a decent sized chunk of ice and not even flinch. If you can get your hands on it, there is a 4 part video series of the original 777 engines being certified which shows the ice ingestion test. It swallowed several feet of around 2 inch thick of ice and made snow cones out back.

[Noise Unit]

Agree with Gas Path

Remember that an important part of engine cert involves the engine swallowing substantial quantities of ice fragments, to represent a hail storm. The 'hail' will also have somewhat higher velocities than shed ice which have a standing start and <5 ft to accelerate.

[411A]

If you have a closer look at some of the earlier RB.211 series engines (-22B, 524B02 for example) you will notice rather blunt spinners.
Simple reason.
They were anti-iced continuously with bleed air.
IMO, a much better idea.

[747FOCAL]

And much louder 411a, a pretty bad idea with a RB211........

[avioniker]

By the way, the rubber isn't all that hard.

[411A]

Oddly enough 747Focal, still stage three...and worked good.

Was staying with a friend some years ago at Morfelden (sp?) just south of the FRA airport, and they had a dB meter just up the street, with a recorder and timer.

B747 departed...full scale
DC-10, likewise, 3/4 scale...ugh!

L1011....supremely quiet, meter barely moved.

LOCKHEED got it right (with proper British engines, of course)...sadly they didn't sell more

[mutt]

411A,

I presume that your little bit of research also discovered the takeoff weight of each aircraft?

What about the additional fuel burn due to the extra bleed air? Surely the rubber nose idea is cheaper?

Mutt.

[Noise Unit]

Bleed air is expensive. You've already paid (in fuel and hence cash) to compress and heat the air and then you're dumping the heat into the spinner. There is also less air to push out the back.

You also have the complexity and system weight of transferring the hot, high pressure air forward into the spinner and then finding somewhere to dump it without creating further losses in the gas path.

Pointy spinners also look sexier.

Avionicar - I've seen some pretty hard looking rubber for sale in select Amsterdam retail outlets.

[lomapaseo]

I see this has diverted into bleed air

I'm not sure where the trent gets it's air from to go into the spinner, but Pratt gets it from the last bearing compartment in the turbine. That air is just warm enough that it screws forward inside the fan drive shaft (some obscure guy discovered a heat pump screw effect under these conditions.)

All one had to do was to twiddle with the drain holes (for water condensation and oil leaks) in the spinner to let the air flow just enough to keep the ice sheath covering down to a minimum.

The heat flux is minimum until the ice actually forms and creates a surface insulating blanket to raise the skin temperature of the spinner high enough to shed the ice. Certainly not a big performance hit on the engine air.

[411A]

Mutt,

All were rather heavy.

LH 747 to ORD

NW DC10 enroute USA

UL L15 nonstop CMB. (Had personally operated this aircraft into FRA earlier that day).

These dB meters were all around the FRA airport housing sites, and could be clearly seen by passersby. Of course, when a BAC111 departed, many of the meters had to be replaced, due to the fact that the needles were bent 'round the top scale stop... ....or so it seemed

[dartman]

Having said all that about the RB-211, I was told that RR orginally did, and / or planned to certify it on the 747 without deicing it. P&W / GE objected ( unfair compedative advantage etc. due to the aforementioned fuel issues ) so RR relented, and certified it with. The spinner explanation seems plausable, but what about the ice forming on the nacelle. Anyone have anymore background on this?

[Night Las Palmas]

A friend at Rolls Royce assures me that it's not a hard rubber point but a " Dynamic Anti Ice Shedder" or some similar fancy title.

[gas path]

"Dynamic Anti Ice Shedder"

Sounds about right, but at the end of the day it's still a hard rubber tit!

dartman
The original 211 spinner was indeed anticed fulltime with a bleed from ip4 compressor, when the d4 came along it was dispensed with. However the engine nacelle has always had an anti-ice facility, hp or ip air depending on thrust level.

[dartman]

Thanks, and yes I certinly meant anti not de-iced. So even on the early version, there was a NAI switch?

dartman