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-   -   T-Tail Icing (https://www.pprune.org/tech-log/225210-t-tail-icing.html)

speedrestriction 9th May 2006 11:02

T-Tail Icing
 
Are T-tails more prone to icing than conventional tail arrangements. If so why?

Old Smokey 9th May 2006 12:48

Until someone comes up with a well informed answer (which this is not), my own personal statistics, having spent about equal time on T-Tail and 'conventional' tail aircraft, is that I've had worse tail iceing encounters with conventional tail aircraft than T-tail. In fact, I can't recall any significant tail iceing encounters at all on T-tail aircraft, but had a few wide eyed moments with conventional tail, particularly in your part of the world!:eek:

Regards,

Old Smokey

Mad (Flt) Scientist 9th May 2006 14:49

There's really two parts to the question: are T-tails more susceptible to ice accretion; and are T-tails more sensitive to ice accretion.

For the first question, a T-tail would appear to be completely 'unshadowed' while there is a small amount of geometrical shadowing possible for a low-mounted tail, due to it being behind the wing. This effect is probably relatively minor, though.

Also, one might expect, all other things being equal, that a T-tail may be slightly smaller than a low-tail, which would tend to make it a better ice catcher. (On a swept fin, a T-tail may be slightly further aft, allowing a smaller area for the same tail volume, plus the fflow field at the top of the fin may allow a smaller tail for the same effect; countering these somewhat, a T-tail aircraft often has a shorter fuselage aft of the wing - due to the engine effect on cg - than a low tail aircraft, which would cause the T-tail to be larger in that case.) My own guess is that the T-tail ends up being slightly smaller overall from these effects, but I doubt it is a big factor.

In terms of sensitivity, again the size of the tail will have an effect (smaller surfaces being more impacted by a given ice catch) so any tendency for a smaller size will have an effect here also. I doubt if there's any other systematic design effect that would heighten sensitivity of either design.

captainpaddy 9th May 2006 15:07

The increase of ice accretion on a surface that is experiencing the effects of turbulent airflow is (apparently) very significant. I would suspect that the T tail being further from any disturbed airflow from the main wings would be advantageous. Your experience seems to agree.

XPMorten 9th May 2006 16:05

Sometimes, having a T-tail also means you have rear mounted engines.
Ice from the main wing can then fall off and get sucked into the engine.
Has happened on a few occations... .

M

speedrestriction 9th May 2006 17:48

Thank you, one and all. You should probably charge for this level of expertise!

oldebloke 9th May 2006 20:24

As far as I can recall the 727 had no tail deicing(unlike Douglas, Boeing built the larger horizontal stab area to support the weight)..On the DC8 one had to give a 'shot' of tail deice(3 min) prior to shutoff at the Outer marker..
The A320 had no tail deice fitted..
Cheers:ok:

Mad (Flt) Scientist 10th May 2006 02:25


Originally Posted by XPMorten
Sometimes, having a T-tail also means you have rear mounted engines.
Ice from the main wing can then fall off and get sucked into the engine.
Has happened on a few occations... .
M

Pretty much restricted to icing on top of the wing, accumulated on-ground. It's pretty much impossible for ice to form there in-air.


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