What is the difference between anti-ice and de-ice systems?

An anti-ice system prevents ice from forming on the protected surface and operates in steady state, leaving residual water that can run back. A de-ice system lets ice form and then melts or expels it in cycles, so it operates in a transient state.

What do running wet and fully evaporative mean?

In a fully evaporative anti-ice system all impinging water evaporates on the heated surface, which needs the most power. In a running wet system the surface stays above freezing while water runs aft, and the design must show where that water refreezes and that the ice there is acceptable.

Can you size an electrothermal ice protection system by simulation?

Yes, for the thermal design. We compute the heat balance between air, water film and skin, including conduction through the heater and structure layers, and deliver surface temperature, wet and dry limits, runback and power density. Final proof still needs icing tunnel or flight tests, and simulation reduces how many are needed.

Do you analyze pitot and air data probe heating?

Yes. Probes and sensors are part of our scope. Pitot probes are qualified by TSO-C16b and ETSO-C16, which call SAE AS5562, rather than only by FAR 25 Appendix C or O. We presented a probe power density model at SAE AC-9C in 2010 and compared it with FAR 25, EASA, BS 2G 135 and SAE AS5562 conditions.

How does simulation reduce icing tests?

Simulation designs the system, supports coverage of the envelope and of failure cases, and reduces the number of icing tunnel and flight test points. Tests then validate the numerical tools at the points that matter. Once validated against icing tunnel and flight data, simulation can also cover atmospheric icing conditions that were not tested, rare conditions and the edges of the envelope.

Is our design data kept confidential?

Yes. We work under NDA. In consultancy you receive results and reports, and your geometry, materials and heater layouts stay with you.

Services / Icing and aircraft systems / Ice protection

Ice protection engineering: anti-ice and de-ice design, testing and certification

We design, test and certify ice protection systems. Sizing and verification use coupled CFD: airflow, droplets, water film, evaporation, runback and heat conduction through the structure. The method comes from ten years of anti-ice design and certification at Embraer and is compared with NASA anti-ice experiments.

Request a technical proposal See the evidence

Led by Dr. Guilherme A. Lima da Silva: anti-ice design and certification of wings, pitot, TAT, static port and smart probes at Embraer (1997 to 2007), with tests in the NASA icing tunnel. His 2007 Journal of Aircraft papers on airfoil anti-ice simulation remain his most cited.

Heater power density60 %

Protected length aft of the leading edge8 %

Relative total power (density × length)0.60×

Running wet. The surface stays above freezing. Water runs aft of the heater and can refreeze as a ridge. At the same power density, a longer heater only moves the ridge aft. Only more power density shrinks it.

Qualitative sketch of the trade-off. Power density is a share of the level that evaporates all impinging water. Extending the heater at the same power density does not remove the residual ice, it moves it aft and raises the total power. It is not a simulation result.

IndustryEmbraer, 1997 to 2007: anti-ice design and certification for the wing and for pitot, TAT, static port and smart probesSlat and wing thermal anti-ice with LEWICE and the NASA icing tunnel. Smart probes certified with CFD++, ahead of TSO-C16b.
IndustryEngine anti-ice system developed with tests and simulationSAE technical paper, 2007, with the Embraer team.
ProjectAkaer STC on a surveillance aircraft: ice protection (FENSAP based) development, simulation, testing and certificationFour-year complete package for supply to Turkish Aerospace (TAI). Certification reports ready for submission.
ProjectJoby eVTOL and an LWC probe redesign: heat load, water catch and optimum heater powerAir data probe for cruise during icing escape, and an electrically heated LWC probe validated in an icing tunnel.
ResearchAir data probe power density model, SAE AC-9C Portland, 2010Compared FAR 25, EASA, BS 2G 135 and SAE AS5562 conditions.
iceAccretionFoamOur 3D solver iceAccretionFoam will add thermal protection in Phase 2FAPESP PIPE, 2027/28. Product development, separate from the project experience above.

Complete packages, from design to certification reports

We prefer whole, long-term programs to isolated runs: ATS4i responsible for the ice protection design, the tests and the certification evidence.

What a package covers

Ice protection design, sizing and integration; test planning and execution in the icing tunnel, on the ground and in flight; and the certification documents, ready for submission to the authority. We issue them ourselves, whether from analysis or test results: system description, safety assessment, certification plan, reports or any other document the program needs. You review them and submit them to the authorities. This is our differentiator.

One team for the whole program

The same engineers carry the program from the first analysis to the last report, so design decisions, test points and evidence stay consistent over the years. Simulation runs inside this work, it is not the product.

An example: Akaer, ASOJ TAI

2020 to 2024. A complete package for a surveillance aircraft, outsourced by Akaer to ATS4i for supply to Turkish Aerospace: ice protection development and simulation, tests, and all certification reports ready for submission.

How a project happens

A program runs through five certification reports: system description; safety assessment; certification plan; icing-tunnel and flight test planning and results; and numerical model description, validation and results.

Need only a part? We define the scope with you.

Anti-ice and de-ice, and where the ice goes

The two families behave differently, so the analysis and the evidence differ.

	Anti-ice	De-ice
Purpose	Prevent ice from forming on the protected surface.	Let ice form, then melt or expel it.
Operation	Steady state, on during the icing encounter.	Transient, in cycles of accretion and shedding.
Water	Residual water forms and can run back and refreeze aft of the protected area.	Melt water and shed ice pieces.
What we analyze	Surface temperature, wet and dry limits, runback and refreeze location, power density and margin.	Cycle timing, ice thickness at activation, residual ice and where shed pieces go.
Typical hardware	Hot air from bleed, electrothermal heaters.	Pneumatic boots, electrothermal cycles, electro-expulsive systems.

Thermal systems are the most common on commercial aircraft. New systems may use hydrophobic surfaces or electro-expulsive de-ice, and we model those as well as mechanical protection.

Ice protection is a systems problem

It touches other systems

Ice protection connects to pneumatic, electric, indication, navigation and stall protection systems.

It must not interfere

Its operation cannot degrade those systems, and they must be evaluated under icing conditions.

It needs operating rules

Flying in icing conditions requires specific maintenance and operation procedures.

The IPS has multiple interfaces with aircraft systems and requires specific procedures for operation.

Dr. Guilherme A. Lima da Silva, The Icing Engineering Process

The physics we solve

Five layers from the free stream to the skin, solved together.

1
Free stream flowSpeed, altitude and angle of attack from the mission.
2
Gaseous flow with dropletsAir and water vapor mixture. Droplet trajectories and impingement.
3
Momentum and thermal boundary layersIntegral or differential solution, or CFD with heat transfer, with laminar-turbulent transition and streamwise gradients.
4
Water filmBeads, film and rivulets. Evaporation, energy balance and runback.
5
Solid surfaceConduction through skin, heater and structure layers.

Effects that decide the answer

Laminar-turbulent transition, streamwise temperature and pressure gradients, and the hydrodynamics of runback water all change temperature and evaporation, so they are in the model.

What you receive

Surface temperature, water mass flow, wetness, runback limits, power density and margin, and the residual ice left when the system fails or is off.

One CFD tool for all five layers

All of this physics can be solved inside a single CFD tool, such as iceAccretionFoam, CFD++ or FENSAP-ICE. It is separated into layers here only for clarity.

Tools, and how mature each one is

We say what runs today and what is still in development, so you can plan the evidence.

Tool	Role in ice protection work	Status
ATS4i thermal codesATS4i, 2D	Integral (Ambrok and superposition) and differential boundary-layer methods coupled to a water film with beads, film and rivulets. Compared with the NASA anti-ice experiment of Al-Khalil et al. (2001).	In use
CFD++Metacomp	CFD with heat transfer: external flow, droplets and thermal balance on the wall, plus internal hot-air flow when the system needs it.	In production use
LEWICE and LewIntNASA, American Kestrel	Fast thermal analysis of anti-ice and de-ice heat balance. ATS4i holds a LewInt licence.	Licensed
FENSAP-ICEAnsys	Ice protection module on a licence you provide, as on the Akaer STC ice protection work where the customer required it, compared with the other tools when a cross-check helps.	Client-supplied licence
iceAccretionFoamATS4i, foam-extend 5.0	Finite-area water film exchanging heat with the wall, and 2D shell conduction for electrothermal heaters, in the same 3D solver that grows the ice.	Phase 2 target, 2027/28

Air data probe envelope mapping

Makers of pitot, TAT and smart probes, angle-of-attack vanes and ice detectors are a large market, with hundreds of suppliers in the US alone, and their certification depends on conditions that differ from standard to standard. We map them.

Power density needed to keep the probe skin at 5 degrees Celsius against water catch, with the FAR 25 critical envelope and crossing points, EASA conditions, BS 2G 135 tests, SAE AS5562 tables 2 and 3 and reference points — Heat load against water catch: power density needed to keep the skin at 5 °C, with the FAR 25 continuous and intermittent maximum critical envelope and crossing points, the EASA conditions, the BS 2G 135 tests, SAE AS5562 (Class 1, tables 2 and 3) and the reference points.

Static air temperature against pressure altitude at 145 knots calibrated airspeed cruise, with continuous and intermittent maximum envelopes, the aircraft limit and crossing points with liquid water content — Operating points: static air temperature against altitude at 145 KCAS cruise, with the FAR 25 continuous (CM) and intermittent (IM) maximum envelopes, the aircraft limit, and the crossing points for recovery temperatures of 0, −5, −10 and −16 °C, each with its liquid water content.

What the mapping does

Python programs place the operating points of your aircraft and the icing tunnel test points on the same heat load against water catch plane as the old and current standards: FAR 25 Appendix C, EASA, BS 2G 135 and SAE AS5562, which FAA TSO-C16b calls. You see which conditions drive the heater power and which tests are worth running. The method started as a spreadsheet model presented at SAE AC-9C in Portland, with a lumped heat and mass balance, ice crystal and water catch terms and CFD++ collection efficiency (presentation). It now runs as Python programs.

Why probes have their own standard

Pitot probes are qualified by TSO-C16b, which calls SAE AS5562, and by ETSO-C16, not only by FAR 25 Appendix C or O. On Air France flight 447, in 2009, ice crystals blocked the pitot probes and started the chain of events, according to the French BEA final report.

CFD on the real aircraft

CFD gives the water catch, and the LWC concentration and speed near the probe, and maps the heat load on the heater. We did this for an eVTOL air data probe that had to be certified for cruise during the escape from icing conditions.

Pitot probe standards and our certification

Pitot probe qualification moved from a 1948 airspeed tube specification to the ice and rain conditions of SAE AS5562, which FAA TSO-C16b calls since 2017. Our Embraer smart probe certification answered an EASA CRI in 2003 and 2004, before the FAA and EASA standards reached those liquid water conditions. Select a milestone to read the detail.

Dec 1947
SAE AS393, the first pitot heater standard
SAE AS393, Airspeed Tubes, Electrically Heated. Revised in 1960 and declared noncurrent in 2002.
1 Sep 1948
FAA (then CAA) TSO-C16, first edition
FAA (then CAA) TSO-C16, Airspeed Tubes (Electrically Heated), first edition, with the performance requirements of SAE AS393. Record: FAA TSO-C16, Accuris
1967
British Standard BS 2G 135 with supercooled water tests
British Standard BS 2G 135, Electrically-Heated Pitot and Pitot-Static Pressure Heads (Amendment 1 of 1973), with the supercooled water tests of section 8.7.
24 Oct 2003
EASA ETSO-C16, based on SAE AS393
EASA ETSO-C16, based on SAE AS393. Document: EASA ETSO-C16
2003–2004
Embraer E170/190 smart probes: EASA CRI answered
Embraer, E170/190: the EASA CRI for the smart probes is answered with the AS5562 liquid water conditions, more than a decade before TSO-C16b, using simulation and CFD++. The E170 was validated by EASA on 20 February 2004 (EASA type certificate data sheet).
6 Oct 2006
FAA TSO-C16a adds the icing tests and BS 2G 135
FAA TSO-C16a: moves from SAE AS393 to SAE AS8006 (1988) and adds the icing test of 14 CFR 25 Appendix C intermittent maximum, plus the BS 2G 135 supercooled water tests 1 and 2 of paragraph 8.7.2.
14 Oct 2009
EASA ETSO-C16a, harmonised with the FAA
EASA ETSO-C16a (ED Decision 2009/014/R), harmonised with FAA TSO-C16a after the Air France 447 accident, with the same BS 2G 135 icing test, section 8.7. Documents: EASA ETSO-C16a, EASA terms of reference
Feb 2016
EUROCAE ED-225, the counterpart of SAE AS5562
EUROCAE ED-225, with the same title and scope as SAE AS5562: ice and rain minimum qualification standards for pitot and pitot-static probes.
27 Jan 2017
FAA TSO-C16b calls SAE AS5562
FAA TSO-C16b: calls SAE AS8006A and SAE AS5562, in place of the British Standard. Document: FAA DRS, TSO-C16b
21 Feb 2018
EASA ETSO-C16b, based on the FAA TSO-C16b
EASA ETSO-C16b (ED Decision 2018/002/R), based on FAA TSO-C16b. Document: EASA ETSO-C16b

Evidence you can check

Client and Embraer project work, and the papers behind the method.

Project work

Project	What we did	Tools and tests	Result or venue
Akaer STC, surveillance aircraftProject	Ice protection development, simulation, testing and certification inside a four-year complete package for supply to Turkish Aerospace (TAI). ATS4i was responsible for design, test and certification.	FENSAP-ICE, as the customer required.	Certification reports ready for submission. 2020 to 2024.
Joby (eVTOL) air data probeProject	Heat load mapping on the probe for cruise during escape from icing conditions.	3D CFD water catch, LWC concentration and speed near the probes.	Python programs for operating and tunnel test points against SAE AS5562, and certification support. 2023 to 2024.
LWC probe redesign, Droplet Measurement TechnologiesProject	CFD and ice protection analysis for the best electrical heating design of an LWC probe.	CFD for Cp and impingement, electrical anti-ice code, icing tunnel tests to validate the code.	Optimum heating power distribution on the probe.
Zodiac Aerotechnic: ice detector shapeProject	Shape optimization of an ice detector to weaken the shock wave and increase convective heat transfer, so the heater works better.	CFD on several candidate shapes.	Best heat transfer coefficient selected, drag minimized, shock wave weakened.
Embraer: smart probes certificationIndustry	Certification of the E170/190 smart probes. The response to an EASA CRI anticipated, in 2003/2004, the liquid water conditions of SAE AS5562, which TSO-C16b only included more than a decade later.	Innovative approach with intensive use of simulation and CFD++.	E170/190 programs, 2003 to 2004.
Embraer: wing (slat and wing anti-ice)Industry	Design and certification of the thermal anti-ice of the slat and wing, and of the pitot, TAT and static port probes.	LEWICE simulation and tests in the NASA icing tunnel.	1997 to 2007.
Embraer: engine anti-iceIndustry	Engine anti-ice protection system developed with experimental and numerical approaches.	Tests and simulation.	SAE technical paper, 2007.
Pitot tube, A-4 Skyhawk, Brazilian NavyProject	Water collection on the pitot tube. The distribution feeds 1D or 2D heater models.	CFD++.	Peak β of 0.916.
Air data probes: heat load and envelope analysisProject	Python programs that define the operating points and the icing tunnel test points, compared with old and current standards: FAR 25 Appendix C, EASA, BS 2G 135 and SAE AS5562, which FAA TSO-C16b calls.	Python programs: heat load against water catch and operating points.	Used at Joby and presented at SAE AC-9C.
Icing tunnel and pitot tests at UFRJProject	Design and installation of the first icing tunnel in Brazil, pitot icing tests in flight and in the tunnel, and the investigation of the Air France 447 accident.	Icing tunnel, flight tests and thermal models.	J. Braz. Soc. Mech. Sci. Eng., 2016.
Anti-ice model against NASA experimentResearch	Surface temperature and heat transfer coefficients against the experiment of Al-Khalil et al. (2001).	ATS4i integral and differential boundary-layer models.	AIAA, 2009.

Where the model comes from

The thermal balance couples the skin, the water film and the air: conduction along the wall, heat exchange with the water, droplet enthalpy and kinetic energy, and evaporation. It was built during a Ph.D. supported by Embraer and extended with Cal State Long Beach.

Papers behind the method

What we protect

Wings and empennage

Electrothermal, hot-air and boot systems on leading edges and balance horns.

Engine inlets, ram air and propellers

Ingestion risk, lip heating and blade or spinner protection.

Air data probes and vanes

TAT, pitot and smart probes, angle-of-attack vanes and ice detectors, with heater power and location.

Windshields

Heating for the pilot’s view, with layer stack and temperature limits.

Antennas and radomes

Protection that does not disturb the electromagnetic function.

eVTOL, drones and rotors

Aircraft that may have no conventional system and must show that ice does not affect operation, or that they can escape the condition.

Tests and simulation work together

Tests you will still need

Wind tunnel with simulated ice for aerodynamics, icing tunnel for the protection system, artificial-ice and natural-icing flight tests, and tests that validate the results.

What simulation does for the campaign

It designs the system, saves tunnel and flight tests, supports coverage of the envelope, supports certification and supports the analysis of failure cases.

Where the experience comes from

Ten years of anti-ice design and certification at Embraer, then client projects at ATS4i, together with research and the development of our own solver.

Industry Embraer, 1997 to 2007Project ATS4i client and facility projectsResearch Papers, workshops and committeesiceAccretionFoam Development of our own 3D solver

1997–2007
Industry
Embraer: design and certification of anti-ice for the wing and for pitot, TAT, static port and smart probes, with tests in the NASA icing tunnel and simulation.
E190: pneumatic system, ECS and the icing certification, with its wind tunnel and flight test campaign and reports. E145: probe technical support, ADs, service bulletins and flight manual. E170/190: smart probes certification, an innovative, simulation-intensive job with CFD++, answering an EASA CRI that anticipated in 2003/2004 the liquid water conditions of SAE AS5562, which TSO-C16b only included more than a decade later. Slat and wing thermal anti-ice with LEWICE simulation and tests in the NASA icing tunnel. Also the 2001 probe certification process with manufacturers and authorities, and an engine anti-ice system (SAE, 2007).
2003
Research
Airfoil anti-ice system modeling and simulation, AIAA 41st Aerospace Sciences Meeting.
2006–07
Research
Water film breakdown and rivulet model, and two Journal of Aircraft papers on airfoil anti-ice.
2007
Project
ATS4i begins engineering, testing and certification services supported by simulation, with icing and ice protection projects on probes, wings and eVTOL.
2009
Research
At Cal State Long Beach, integrated Cebeci’s compressible differential boundary-layer method into his anti-ice code, with the runback water flow.
AIAA paper with Profs. Hefazi, Chen and Kaups.
2010
Research
Air data probe power density model, SAE AC-9C, Portland.
2011–15
Research
Rough-wall heat transfer wall functions, then CFD and boundary-layer models with transition validated on a rough cylinder.
2016
Project
Pitot icing in flight and in the icing tunnel designed for UFRJ, with the thermal analysis of anti-icing in velocity sensors and structures.
2020–24
Project
Akaer STC on a surveillance aircraft: ice protection (FENSAP based) development, simulation, testing and certification, in a complete package for supply to Turkish Aerospace (TAI).
2023–24
Project
Joby (eVTOL): air data probe heat load mapping and 3D water catch, with icing certification support.
2023
Research
Coupled heat and mass transfer for airfoil ice protection systems, published on the ATS4i blog.
2026–28
iceAccretionFoam
iceAccretionFoam: FAPESP PIPE Phase 2 targets thermal protection in the 3D solver.

How an engagement runs

Mission and performance
Mission profile, weights, speeds and altitudes. Angle-of-attack ranges from flight dynamics.
Baseline ice and critical conditions
Ice on the unprotected surface and the critical points of the envelope.
System design
Architecture, heat source, layers, protected area and control logic with your team.
Thermal analysis
Heat balance, water film, runback and power density at the critical points.
Failure cases and residual ice
Ice shapes when the system fails or is off, and the residual ice after de-icing.
Certification reports and test support
System description, safety assessment, certification plan, and reports of the numerical model and of the icing tunnel and flight tests. All under NDA.