GE Measurement & Control

Introduction to Pitot Static Testing

Contents 01. Introduction 02. Science behind Pitot Static Pressure 03. Connecting Air Data Test Sets to Pitot Tubes 04. Remove Before Flight 05. Connecting to the Pitot Tube 06. Understanding Multiple Connection Ports 07. Measurement Accuracy 08. Leak & ERP Testing The Air Data Test Set in essence simulates altitude, rate of climb and air speed. An ADTS is seemingly able to ‘fly’ the aircraft on the ground, even if you want to fly faster than the speed of sound!

Introduction His theory also works for air The pressure of the free stream An Air Data Test Set (ADTS) or pressure and other gases and so air (Ps) is the same as the ambient Pitot Static Tester is a piece of a modern version of his simple air all around the aircraft. This equipment used to test aircraft measurement tube is now fitted ambient ‘barometric’ pressure flight instruments while the to virtually every aircraft and is decreases with increasing aircraft is on the ground. Many a called a Pitot Tube System. The atmospheric altitude. The instruments in an aircraft’s mathematical principles of his Static (Ps) pressure is inversely cockpit are based on measuring system are well explained by this proportional to aircraft altitude. various pressures from the air eFunda article at http://tinyurl. around the plane when it is com/5rztn. An overview of how an A great web based Pitot Static in flight. By using a precision aircraft’s Pitot system works is as Simulator has been created by pressure controller to recreate follows. Luiz Roberto Monteiro de Oliveira. specific flight pressures at sense points on the outside of the The forward opening point of the You can experiment with Pitot aircraft’s skin, engineers can Pitot (Pt) tube receives air at a and Static pressures and see the create a simulated flight for the higher ‘impact’ pressure than the effects on aircraft instruments. cockpit instruments and test that side facing Static (Ps) tube that Visit http://tinyurl.com/p64v5q8. these vital safety systems are senses the free stream air. working and correctly calibrated, The difference between these ready for the next flight. two pressures is known as the dynamic pressure (Qc) and is The air data test set in essence proportional to aircraft’s Indicated simulates altitude, rate of climb, Air Speed (IAS), also known as air speed and rate of acceleration. Calibrated Air Speed (CAS). The ADTS is seemingly able to ‘fly’ the aircraft and even if you want to fly faster than the speed of sound at Mach 2, an ADTS can handle it!

Science behind Pitot Static Pressure The science of aviation air data measurement was discovered by the French hydraulic engineer Henri Pitot (1695 - 1771). Henri’s prime interest was measuring the velocity of water in the river Seine, but his Pitot tube design proved to be more useful than simply measuring a liquid’s velocity. Connecting Air Data Test dynamic pressure always requires B) Alternative style adaptors are Sets to Pitot Tubes a forward facing probe and available that use vacuum suction the adaptor will be of simpler cups to gain a grip of the aircraft The aircraft Static and Pitot ports construction. Sensing the Static or surface in order to press the are designed in a number of ambient pressure always requires port connection seal around the different styles, some of which a side facing port or one that is groups of holes. These may either may be specific to a particular protected from the impact air use over-centre suction clamps aircraft type. Making a piped encountered in forward flight. or use an external source vacuum connection to test the pitot This is often seen as a small line to apply continuous suction system will usually require a pattern of ‘pepper pot’ like holes, to the fixing cups. The over special pneumatic connection flush with the skin of the aircraft fixture or Pitot Static adaptor. centre clamps can only be used in order to create minimum air successfully on totally smooth Where the two ports are turbulence in that region. Making areas. combined within the one probe robust connection to such a port then a combined port adaptor is is more of a challenge, since there There is such a wide variety of employed. The adaptor is pushed are no obvious metal points to Pitot Static port arrangements over the probe and locked in grasp! position with compression rings. It on different aircraft today that it contains precision seals to create Two methods are possible. would be difficult and expensive partitions between the Pitot and to provide a suitable array of Static openings on the probe A) A special ‘Clico’ style adaptor adaptors with every ADTS sold. surface. is available with an outer ‘O’ ring Specialist companies provide seal large enough to encompass these parts to the industry. They Sometimes the Pitot and Static the entire hole pattern, and will either be supplied with each connections are found on has an extendible prong (like an aircraft as they enter service or different places on the aircraft’s expanding syringe needle) that is can be purchased as a matching surface, so the two connections inserted through the centre hole adaptor set for a known aircraft must then be made using and used to pull down the adaptor type. separate adaptors for each seal against the aircraft surface. function. Sensing the Pitot or WHY CALIBRATE? • To comply with regulation • To maximize process performance • To maintain safety • For quality control

Remove Before Flight Understanding Multiple and First officer are now often Whilst the aircraft is on the Port Connections Electronic Flight Instrument ground you will often see brightly Trying to apply two simple Ps and System (EFIS) display panels coloured port covers or flags Pt port connections can still be driven by an Air Data Computer hanging from the Pitot Static a little bewildering when faced (ADC) that actually measures ports. These are fitted not only to with a real aircraft. It rapidly the port pressures and then protect and warn airport staff and becomes apparent that all large processes and presents these as service engineers not to damage commercial aircraft have more a graphic display. The Standby these relatively fragile structures, than one Ps and one Pt port! In Instrument set is often still a but also to stop the bugs crawling order to create a fail-safe system more traditional pneumatic / inside them on a warm day. for this vital flight information, mechanical design requiring no A spider or fly stuck down a Pitot multiple pressure measuring electrical power to operate. tube could cause a blockage and systems are fed from similar serious airspeed measurement ports placed at different locations Measurement Accuracy errors. It is of course essential on the aircraft surface. It is quite Testing the pitot static system that these intentional blockages typical to have three complete air is obviously critical for the are removed before flight, or data measuring systems installed air data testing, and so they are within one aircraft. These are safe operation of the aircraft. made highly visible with coloured usually referred to as Captain, Numerous Airworthiness tabs and flags. First officer and Standby. Authorities have now adopted policies requiring the integrity and accuracy of altitude Connecting to the Pitot The locations of ports and cross feed routings are designed indicating systems to be verified Tube so that a bird strike or other periodically. This is especially Once the adaptors are in place system failure on one side of important for aircraft flying in on the aircraft ports, suitable the aircraft will not affect all regions with Reduced Vertical length hoses with the correct the critical measuring systems Separations Minimum (RVSM). terminations will be required. simultaneously. The aircraft RVSM allows aircrafts to maintain It is obviously of advantage to air data management systems 1000 feet vertical separation colour code the two connection and flight crew can constantly instead of 2000 feet. Due to this, hoses to avoid mistakes in aircraft compare multiple readings of the Airworthiness Authorities connection. However there is the same critical parameters require errors resulting in the no standard or universal colour and take any necessary steps static system to be closely coding for Pitot Static testing to isolate faulty sub-systems. monitored. Thus, testing and within the aviation industry. In When connecting a ADTS it may calibrating with a highly accurate the majority of the world red for be necessary to blank unused system has never been so vital. Static and blue for Pitot is the port openings on the opposite Engineers should ensure that the common colour code but the USA side of the aircraft. The primary accuracy of any ADTS test set will often operate with blue Static instruments for the Captain delivers compliance with RVSM and red Pitot. performance. Leak & ERP Testing This simulation will also identify GE ADTS 500 series ADTS sets can be used to cover any leakage of interconnecting GE manufactures a range of Air other key tests such as leak sensor pipework. Data Test Sets for large and small testing and Engine Pressure civil and military aircraft. They Ratio Testing (EPR). It is crucial About GE set the standard in accurate and to correct any leak found with GE (NYSE: GE) works on things easy to use air data test sets. the hose connections or aircraft that matter. The best people and More details at: systems before proceeding with the best technologies taking on https://www.gemeasurement. any further testing as it would the toughest challenges. Finding com/test-calibration/pitot-static- interfere with the results of other Solutions in energy, health and testers/adts500-series-air-data- avionics testing. Some ADTS test home, transportation and finance. test-sets. sets offer leak testing, so aircraft Building, powering, moving engineers don’t need to carry and curing the world. Not just multiple tools and can determine imagining. Doing. GE works. the location of the leak by a simple process of elimination. Leak tests avoid the worst case About GE M&C scenario: having a leak whilst GE Measurement & Control is a flying 40,000 feet high. The ability leading innovator in advanced, to do a leak test enables aircraft sensor-based measurement; engineers to determine whether non-destructive testing and the leak is in the ADTS, the inspection; flow and process hosepipes or the aircraft. control; turbine, generator and A more niche form of avionic plant controls; and condition testing is EPR testing. An ADTS monitoring. We delivery accuracy, can be used when the aircraft is productivity and safety to a wide on the ground to simulate EPR in range of industries, including oil & order to validate the cockpits EPR gas, power generation, aerospace, measurement instrumentation. metals and transportation.

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