View Full Version : Icing detection

17th Aug 2004, 03:42
Another quick question. Do airliners have any sort of icing detection probe/s? If so, where are they located and how do they function?



17th Aug 2004, 03:51
I'm not sure if there is such a thing as an icing detector, apart from the good old Mark I Eyeball. The b737 website has an interesting pictorial lesson on how to detect icing.

Ice and Rain Protection (http://www.b737.org.uk/iceandrain.htm)

Old Smokey
17th Aug 2004, 04:27
Yes, some aircraft do have them. For the 2 aircraft types that I've operated which had such a system, a vibrating probe was placed in an ice-sensitive area, and, when iced up, the lower frequency of vibration trigerred an icing alert. This type of system is periodically de-iced by heating, allowing for on-going detection of further ice build-up.

On one type which I flew it was very good, as confirmed by the 'traditional' ice detection procedures. The B777 detection system has an Auto function to activate Nacelle heat etc., but several operators have encountered icing problems undetected by the system, and the Automatic system is utilised as a back-up to more traditional pilot detection and prevention procedures.

There are other types, other posters will no doubt advise.

17th Aug 2004, 06:01
Yep, the good 'ole TriStar has one (vibrating type, as previously described) and it generally worked OK.

17th Aug 2004, 16:07
we do have on the 737 an ice detecting system,which tells when ice appears,then by another light 'no ice' tells when the ice was eliminated.
the ice detector is on the forward left fusselage,near the data probes.The detector operates by magnetostrictive oscillation (magnetically induced vibration). When ice forms on the probe, it has a different vibrational freq than when it is clean.It works only in flight.It is deiced periodically by internal heaters.
dud: that site is not entirely accurate. Also ice can form on the plane with no visible indication on the windshield.
Brgds Alex

18th Aug 2004, 02:26
Thank you all for your answers.
I was curious to know whether airliners used the same type of icing detection technology (MSO) that is used/being implemented in ground based automated icing detection, and the answer is yes.

Is it safe to assume that ALL airliners are equipped with this technology? 7X7/A3XX/MDXX ? What about regional jets?

In glass cockpits, is there an EICAS icing message that pops up?

On the low-tech side, is anyone aware of aircraft which have specifically designed protuberances that are visible from the cockpit and which were designed with the sole purpose of providing visual icing accretion indication to the pilots?
In small unpressurized pistons, the OAT probe is usually a good indication (by good I mean one that is a good ice accretor). I read somewhere that the "sharper" the object, the more it accretes ice.

Thanks again,


Old Smokey
18th Aug 2004, 04:40

Q1. It is definately NOT safe to assume that ALL airliners are equipped with this technology. Of the 7 jets I've flown in airline service, only 2 had such a system. That doesn't mean that manufacturers haven't back modded older aircraft. 411A, did Lockheed produce the L1011 with this system, or was it a back mod?

Q2. Of the 2 aircraft that I know, there is an EICAS message to advise of icing (even if the message only advises that it has automatically turned the Anti-Ice equipment ON).

Q3. None that I know of, but, all the older Boeings that I flew used ice accretion on the 'large lumpy and ugly' windshield wiper bolt as a good indicator.

Q4. Conventional theory does indicate that sharper objects do accumulate ice more quickly, but, refer back to Q3 regarding 'large lumpy and ugly' windshield wiper bolts.

18th Aug 2004, 04:57
The most common Ice Detection Probe (the vibration type as described above) is made by Rosemount (now Goodrich). It's fitted to all Bombardier aircraft - probably as they're designed to Canadian regs.

Most other aircraft (including the ones with the probes) have wing inspection lights that illuminate the leading edge and are aimed at a part of the airframe susceptible to icing that is painted black so ice shows up. On aircraft with winglets, this is often at the angle between the wing & the vertical winglet.

Flight Detent
18th Aug 2004, 11:23
Hi All,
The ice detector system I am familiar with is fitted to all Lockheed P3s.
It's an aerodynamic probe with a line of 5 or 6 small holes and one larger hole, all subject to normal airflow, the probe is mounted roughly in the same vicinity as your pitot probes, near the nose.
These small/large holes in the probe are cleverly designed to be of the same total area as each other, (the total of all the smaller ones equals the size of the larger), allowing the diaphram inside, sensing between them, to remain centralized.
As soon as ice is detected, the smaller holes ice up quite quickly, forcing the inner diaphram to be displaced, doing two things:
1/ illuminates the 'ICING' light in the flight deck,
2/ turns on a small heater in the probe to melt the ice.

When the ice melts, both the light and heater turn off.

It works brilliantly, and the severity of the icing can be gauged roughly by the rate of the indicator light flashing.



22nd Aug 2004, 09:50
Another airliner installation utilises a rotating shaft which is grooved. In close proximity is a fixed knife edge. Ice accretion will slow or stop the rotation of the shaft due to interference with the fixed edge, triggering an icing warning.

22nd Aug 2004, 14:44
Old Smokey,

The TriStar had the ice detection system fitted as standard equipment...manufactured by Rosemont.

23rd Aug 2004, 01:48
In my experience the only thing that rotating grooved shaft ever did was set off the MWS and startle the crew at the most inopportune time. The best ice detection method on the aircraft I flew equipped with that contraption - HS125 - was the windshield wiper attach bolt. :p

23rd Aug 2004, 08:27
"Is it safe to assume that ALL airliners are equipped with this technology? 7X7/A3XX/MDXX ?"

The 744, comes in lots of different flavours...

Ones without any detecting probes.
Ones with a single ice detector, but manual operation of anti-icing.
Ones with two detectors and a fully automatic anti-ice system (Wing and Nacelle).
Others with detectors, auto anti-ice for nacelles, but not for wings... etc.

The ones with detectors have them mounted on the nose below the pitot/static probes.


FE Hoppy
24th Aug 2004, 13:38
The EMB 170 has two of the vibrating type detectors that will automatically activate the AI systems. They are mounted in such a way as to be visible from the flight deck.

27th Aug 2004, 08:47
palgia, I'm aware of a low tech 'protuberance' that was used on the RAF model of the VC10. I don't know if it was fitted to the civil machines. It consisted of a black aerofoil shaped rod about 6 inches long, sticking out of the fuselage just below the Captain's window. In icing conditions it would ice up and the skipper could see the ice with his Mk 1 eyeball. It had a three position, centre off switch that when operated one way lit a lamp to check the probe at night and in the other position switched on a heater to clear ice off the probe - so you could see if it iced up again. The aircraft also had the rotary detector described above.