Pitot GuardianĀ®

Blockage & Anomaly Detection Sensor System

Embedded solution for all aircraft anemometric sources.

Technology Overview

Technology Overview Technology Overview Technology Overview
Updated 17th March 2019

Bad air data and the confusion that can arise when pilots are presented with information not known to be false, can start a chain of events which may threaten the safety of the aircraft. The technology is designed to be deployed on Total and Static pressure ports & probes. While developing the system I have always had in mind that I want to alleviate this cockpit confusion by presenting clear information that when air speed indication is not correct on one or more air speed indicator (ASI), the pilot can know the moment it is happening and focus on either a good ASI, or refer to the aircraft manual on correct procedures for loss of air speed indication, saving valuable time. An example demonstrating this need for situation awareness can be found in a *UAE GCAA report in relation to Etihad Airways A6-EHF Airbus A340-600 (non-serious incident); that there may be cases where NO ECAM alert is triggered and cockpit indications appear normal whereas they are actually false. As such, flight crews must have in mind those symptoms and be able to detect such a problem. Having a Pitot / static blockage detection sensor embedded in to each ADU would ensure ADR's detect all failures.

Shortly after the loss of Air France flight 447 in June 2009 I set about developing a robust means of detecting anomalies in Pitot static systems which give rise to false air speed data being presented to pilots. I looked at existing efforts in this field and decided that not enough was being done to address the issue, and some attempts were looking at over-complicated or impractical solutions. By late 2009 I filed for a broad patent and had simple working 'proof of principle' prototypes. During 2013 I began liaising with the aerospace industry on how best to proceed and we've been working hard building more and more robust devices all the while shrinking the required hardware and further developing our code to where it is today.

I now have a device which operates using my software in conjunction with a 'single chip' controller and novel sensing method capable of performing all the required tasks involved in monitoring and reporting when blockages or other abnormalities are causing false air speed data. A proprietary algorithm in conjunction with the sensor is able to discern the status of the Pitot and static system, regardless of external acoustic and inertial influences.

Pitot Guardian® technology is designed to be embedded within the aircraft's fuselage mounted air data module (ADM or ADU) from where it continuously monitors the architecture of the Pitot probe all the way to the tip plus a short distance in front of the probe aperture, with various other configuration options such as 'in line' for aftermarket installation to pneumatic systems. The devices have been tested in simulated flight conditions including wind tunnel and vibration analysis, where they continue to operate and report as designed. Capabilities include (but not limited to);  High speed in flight and ground detection of port / probe blockage before start up, early warning of impending blockage, Insect Habitation, Pitot Icing (high altitude and flash), Volcanic ash ingress and erosion or other types of probe damage likely to present false air speed data.

Vibration Testing January 2018
Wind Tunnel Performance Tests July 2017

Patent #GB2478522B (Aircraft Pitot/Static Warning System)
Pitot Guardian­® Is a registered trademark covering our technology for the detection of blockages within aircraft Pitot static systems and the core software controlling the instrumentation for detection of blockages and anomalies within aircraft Pitot static systems.
*UAE GCAA Ref: AAIS Case Reference 05/2013

Contact us for more information .
Nick Haddock
E: nick@nhtechnologies.co.uk
T: +44 (0)1795 555011

Pitot Related Incidents

Pitot static blockage detection sensor - system overview

The following are just some of the many incidents which have been caused either directly or indirectly by Pitot blockage or other pitot / static anomaly. Mostly benign, all costly to the operator, and some catastrophic. ; (Various online sources)

1st December 1974 - Northwest Airlines Flight 6231. Boeing 727 Pitot probes succumbed to atmospheric icing, subsequent loss of reliable air speed data caused the flight crew to lose control and crashed North West of JFK international airport.

6th February 1996 - Birgenair Flight 301 crashed into the sea shortly after takeoff due to unreliable air speed indication. The suspected cause was mud dawber wasp infestation of one of the Pitot probes.

2nd October 1996 - Aeroperu Flight 603 crashed due to unreliable air speed / altitude data having been caused by masking tape covering the ports. This should have been removed after the aircraft was cleaned and waxed.

12th May 2005 - A Midwest Boeing 717-200 suffered temporary loss of control after the crew responded incorrectly to ice build up on the Pitot probes.

19th March 2006 - A Qantas Airbus A300-303 Pilot in command rejected take off after a significant discrepancy was noticed between airspeed indicators. The heavy braking and heat build up caused the tyres' fuse plugs to blow out.

23rd February 2008 - B2 Spirit Bomber crashed in Guam after moisture build up on three of the 24 air pressure sensors caused inaccurate data to reach the flight computer. The flight crew believed they were rotating at the correct speed of 140knts when in fact the speed was 10knts slower. The data also caused incorrect pitch information. The aircraft stalled and veered to the left.

28th January 2009 - A Boeing B752 Astraeus Airlines being operated for Ghana Airways en-route Northern Ghana suffered temporary loss of control being caused by uncertainty regarding the presented air speed. A discrepancy was noticed during the take off roll but the pilot in command decided to continue and deal with the situation later on.

1st June 2009 - Air France Flight AF447 Airbus A330 from Rio de janeiro to Paris exited controlled flight and crashed into the sea. This was attributed to the inappropriate response by flight crew to the transient loss off airspeed indications in the cruise caused by high altitude ice crystals blocking the Pitot probes.

20th April 2012 - Airbus A321-231 Registration G-EUXM encountered atmospheric conditions on two occasions which resulted in temporary loss of reliable air speed data. A PAN Was declared and the aircraft diverted to Stansted for an uneventful landing. While during the events it was not known what was causing the erroneous data due to additional problems being presented to flight crew and the distraction of a bright flash due to electrical discharge phenomena. Pitot icing, it was concluded, was the likely cause of the problems.

21st November 2013 - Etihad A330-200 Flight EY473 Brisbane to Singapore. The pilot in command rejected take off due to airspeed discrepancy. After some troubleshooting back at the gate, another take off was attempted. A discrepancy was once again noted after V1 decision speed, the aircraft rotated and shortly after issued a Mayday. The aircraft returned to Brisbane for an overweight landing. The captains Pitot probe was later found to have been totally blocked by mud dawber wasp activity occuring in just a two hour turn around period.

12th February 2018 - Antonov AN-148-100B operated by Saratov Airlines had departed Moscow's Domodedovo airport en-route to Orsk when it crashed. It is reported, but yet to be confirmed, the Pitot heat had not been switched on as part of the take off check list. The Pitot probes were likely to have been iced up with a loss of reliable air speed information.

(The following three incidents all took place on the same morning and are thought to be all attributed to heavy icing and pitot blockage)

26th February 2018 - Airbus A321-200 Registration HA-LXD Unreliable air speed indication while climbing out of Sofia, PAN Declared. Returned to Sofia.

26th February 2018 - Airbus A321-200 Registration HA-LXL Rejected take off from Sofia at 80 knots due to unreliable air speed indication. The aircraft slowed safely and returned to the apron.

26th February 2018 - Airbus A321-200 Registration HA-LXP While climbing out of sofia the crew requested stop climb at 10,000 feet MSL, Climbed on to 12,000 due terrain, subsequently declared PAN,PAN,PAN reporting unreliable airspeed. Diverted to Budapest for a safe landing.

11th March 2018 - Challenger 604 - Canadair CL-600-2B16 Three crew and eight passengers died when the corporate jet struck a mountainside at 7,500ft after loss or reliable airspeed information initially at FL360 (ASI's diverged). Conditions were severe turbulence with high level icing.

20th July 2018 - Malaysia Flight MH134 Airbus A330-300 was released with all three Pitot covers left in place. After take off, the aircraft safely returned to Brisbane having issued a Pan Pan Pan.