GENERAL DESCRIPTION

Light weight, low cost optical ice-detecting transducer probe detects the first 0.001"  of airframe icing aloft. Thin profile eliminates ram air heating.  Attracts and detects airframe icing instantly upon entering any icing domain, where liquid water changes phase to solid ice. Positive, unambiguous indication of airframe icing conditions before ice becomes a problem on tailplane, wings or struts.  Automates pilots' task of "looking for ice" day or night, while on autopilot, or under heavy workload.  Eliminates guesswork; leaves nothing to interpretation

Provides  useful standard for "known" icing conditions.  Advises pilot to disengage autopilot; activate anti-icing system; activate engine anti-ice; climb, descend, or turn around.  Improves ice detection sensitivity over earlier technologies.  Reduces weight, slashes cost, provides added value to host avionics products.

FEATURES, BENEFITS

AEROSPACE APPLICATIONS

PRINCIPLE OF OPERATION

Ice*Meister Model 9732-OEM ice detecting transducer probe functions as an optical spectrometer. It monitors both the opacity and the optical index-of-refraction of whatever substance is on the probe.

The transducer probe is excited by a microwatt IR LED coupled to the driver plastic optical fiber.  A likewise-IR detector is coupled to the receiver fiber which inputs to an op amp and comparators.

The threshold comparators register the IR signal voltage-analog from the op amp.

NO-ICE state is reported back to the op amp as a stable mid-level signal. When the ice detecting transducer probe enters an icing domain, it can attract either rime ice or clear ice.

RIME ICE  is opaque and milky white, similar to the ice formed in the freezer compartment of a refrigerator that is not frost-free.  Because rime ice is opaque, the transducer probe reports it back to the op amp as a decrease in signal level.  The comparators detect three decreasing levels of signal, analogously ice-alert, more-ice, and saturation-ice, as the IR signal diminishes.  This gives the pilot a rudimentary idea of how fast the rime ice is accumulating.

CLEAR ICE is clear, similar to the ice served in a cocktail glass.  Because of the difference in the optical index of refraction between air (1.0) and clear ice (1.3), the transducer probe reports clear ice back to the op amp as a step-function increase in signal level.  Clear ice normally cannot be seen, thus it is deemed more hazardous than rime ice, and so is logically or'd with the saturation-ice signal.

Icing Research Tunnel test program at NASA Glenn (Cleveland, Ohio) indicates compliance with Society of Automotive Engineers'   aerospace standard AS 5498 "Minimum Operational Performance Specification for Inflight Icing Detection Standards, core paragraph 5.2.1.1.1

Operating characteristics - with NAC reference circuit

Ordering information

Connection diagram

UNIVERSAL INTERFACE BOARD

Model 9733 user interface board is radio silent, has no MHz clock.  Board weighs 1 oz,  measures 1.5" x 4.75", operates to -40 ℃, can be enclosed in a NEMA 4X box, and offers these user features:

Reference schematic block diagram

A brief  note about airframe icing aloft...

The onset of airframe icing formation on a large cross sectional airframe member such as a wing is artificially retarded by compressed-air heat.  The wing collides at high velocity with water vapor molecules in the air, compresses them, and briefly heats them as the wing passes through the domain. 

This heat-pulse may increase the H₂0 molecules' temperature above the latent heat of fusion.  After the pressure dome of the wing leading edge has passed , the molecules relax; give up their dose of  temporary  heat,  and resume their original lower ambient temperature (*).

At that lower ambient temperature, the H₂0 molecules may cool enough to overcome their latent heat of fusion and change state, from liquid water to solid ice.  But by that time, the forward velocity of the aircraft has advanced the wing  past the original point of impact, and the ice forms somewhere aft of the leading edge (**).

A slender (1/4" diameter) transducer probe does not retard the onset of airframe icing because its small cross sectional area compresses fewer air molecules, and heats the surrounding air far less than the leading edge of a thick wing.

Ice*Meister ™ Model 9732 OEM ice detecting transducer probe operates on this principle to attract airframe icing at its earliest (0.001") thickness, and immediately alert the pilot to ice.    

It provides  useful standard for "known" icing conditions.  Advises pilot to disengage autopilot; activate anti-icing system; activate engine heat; climb, descend, or turn around.  Improves ice detection sensitivity over earlier technologies.  Reduces weight, slashes cost, provides added value to host avionics products.

(*) For water, the latent heat of fusion is 80 calories per gram, or 144 BTU per pound.

(**) At 100 knots, the leading edge of an aircraft wing advances 3 feet in 17.7 milliseconds.

(A) transducer probe

(B) transducer probe with short mounting tube

(C) transducer probe with long mounting tube

(D) IR LASER AND IR RECEIVER - one of each used

note: laser channel is white

receiver channel is black

see connection diagram

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Model 9732-OEM?

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