AE-705: Introduction to Flight Pressure & Airspeed Measurement - - PowerPoint PPT Presentation
AE-705: Introduction to Flight Pressure & Airspeed Measurement Part-II Siddharth Joshi Mechanical Engg. Department VIT Vellore AE-705 Introduction to Flight Lecture-06 Capsule-03 Outline Altitude & ROC/ROD Measurement Errors
AE-705 Introduction to Flight Lecture-06 Capsule-03
AE-705 Introduction to Flight Lecture-06 Capsule-03
Altitude & ROC/ROD Measurement Errors in Pneumatic Measurements Measurements in Compressible Flows Non-Pneumatic Measurements
AE-705 Introduction to Flight Lecture-06 Capsule-03
Using pneumatic instruments
AE-705 Introduction to Flight Lecture-06 Capsule-03
Source: http://cormsquare.com//Images/Product/20160316062658667/_03162016062658667_58d0dc8a-08b0-4bfe-b52b-c441dca78856.jpg
used to measure the altitude of an
is supplied with Pstatic from the static ports altimeter shows the pressure directly as an altitude above mean sea level
Source: https://s-media-cache-ak0.pinimg.com/736x/2f/b2/d0/2fb2d079d23f32df9574b6c02eec46ab.jpg
AE-705 Introduction to Flight Lecture-06 Capsule-03
a stack of sealed aneroid diaphragms expand and contract as the pressure rises and falls Kollsman window used to calibrate the instrument to the local altimeter setting A pointer moves on the barometric scale giving the reading
Source: https://www.americanflyers.net/aviationlibrary/instrument_flying_handbook/images/Chapters%201%20to%207_img_80.jpg
AE-705 Introduction to Flight Lecture-06 Capsule-03
Source: http://sarasotaavionics.com/images/productimages/UMA/T8-310.jpg
Measures the rate of descent or climb
detects the change in air pressure as altitude changes VSI is used to ascertain that level flight is being maintained
Source: https://s-media-cache-ak0.pinimg.com/736x/2f/b2/d0/2fb2d079d23f32df9574b6c02eec46ab.jpg
AE-705 Introduction to Flight Lecture-06 Capsule-03
Source: https://upload.wikimedia.org/wikipedia/commons/thumb/4/46/Faa_vertical_air_speed.JPG/220px-Faa_vertical_air_speed.JPG
has a thin sealed diaphragm connected to the static port Calibrated leak to control Pstatic VSI dial returns to zero to show level flight Sealed instrument case
AE-705 Introduction to Flight Lecture-06 Capsule-03
Leading to wrong readings / Crashes !
AE-705 Introduction to Flight Lecture-06 Capsule-03
If the pitot tube becomes blocked, the system will give frivolous reading Contaminants in the pitot tube
Source: https://i.stack.imgur.com/imdrz.jpg
AE-705 Introduction to Flight Lecture-06 Capsule-03
If the static port becomes blocked and the pitot tube remains operable, the airspeed indicator will barely work and readings will be inaccurate The altimeter will freeze in a place where the blockage occurred VSI will indicate zero Blocked static port
Source: http://i.imgur.com/ptfYbcV.jpg
AE-705 Introduction to Flight Lecture-06 Capsule-03
One of the aircraft's three pitot tubes was blocked by a wasp’s nest Auto-pilot system calculated that the plane was travelling too fast The left engine quit first, and then the airliner went into a full stall and crashed into the Caribbean Sea
Source: http://www.computerweekly.com/news/1280096929/Crash-One-Birgenair-Flight-301
Auto pilot raised the nose to slow it down
Source: http://www.airlive.net/onthisday-in-1996-birgenair-flight-301-crashes- shortly-after-takeoff-from-puerto-plata-dominican-republic/
AE-705 Introduction to Flight Lecture-06 Capsule-03
High Subsonic, Transonic and Supersonic Flows
AE-705 Introduction to Flight Lecture-06 Capsule-03
𝟑
𝟑
AE-705 Introduction to Flight Lecture-06 Capsule-03
Source: http://nptel.ac.in/courses/101103004/module7/lec6/3.html
Source: http://www.efunda.com/designstandards/sensors/pitot_tubes/images/Pitot_tube_Mouth.gif
Velocity can be calculated using :
𝛅−𝟐 𝛅
𝟑 𝛅 𝛅−𝟐
Mach number of free stream
AE-705 Introduction to Flight Lecture-06 Capsule-03
The characteristic feature of a supersonic flow is the formation of a shock wave introduction of a Pitot probe leads to a detached bow shock
Source: http://nptel.ac.in/courses/101103004/module7/lec6/images/23.png
AE-705 Introduction to Flight Lecture-06 Capsule-03
Rayleigh-Pitot formula for supersonic flows
02
∾
𝛿 𝛿−1
1 𝛿−1
stagnation pressure of the normal shock Free stream static pressure
Source: https://s-media-cache-ak0.pinimg.com/736x/2f/b2/d0/2fb2d079d23f32df9574b6c02eec46ab.jpg
AE-705 Introduction to Flight Lecture-06 Capsule-03
The Rayleigh-Pitot formula represented graphically
Source: http://nptel.ac.in/courses/101103004/module7/lec6/3.html
AE-705 Introduction to Flight Lecture-06 Capsule-03
Why are pitot tubes shaped like this?
Source: https://thumbs.dreamstime.com/x/d-pilot-thinking-render-50306654.jpg Source: https://s-media-cache-ak0.pinimg.com/736x/2f/b2/d0/2fb2d079d23f32df9574b6c02eec46ab.jpg
AE-705 Introduction to Flight Lecture-06 Capsule-03
position error → Pstatic, local – Pstatic, ambient An “aerodynamic-compensation” pitot tube has a contoured shape
Masud J., Performance characteristics of flush angle-of-attack measurement system integrated on a pitot tube, Engineering Applications of Computational Fluid Mechanics, 2010 Jan 1; 4(4):549-57
AE-705 Introduction to Flight Lecture-06 Capsule-03
Source: https://www.researchgate.net/profile/Imran_Afgan/publication/269062238/figure/fig2/AS:392309884637187@1470545373346/Figure-2-Computational-mesh-in-the-vicinity-of-the-Pitot-tube-oblique-view-only.png
Angle of attack (AOA) sensors measure Pstatic difference between top and bottom surfaces
AOA
As AOA ↑ ↔ Pstatic difference ↑ Employed in supersonic fighter aircraft
AE-705 Introduction to Flight Lecture-06 Capsule-03
Source: Moir and Seabridge, Aircraft systems, Pneumatic systems
Converts air pressure from a Pitot tube or a static port into numerical information System connected together with a data bus ADM → Flexible and modular can be installed anywhere AIR DATA MODULES
AE-705 Introduction to Flight Lecture-06 Capsule-03
Current Developments
AE-705 Introduction to Flight Lecture-06 Capsule-03
Source: http://www.wermac.org/images/orificeflow.gif
Direct air through a plate with a hole Measure the amount of air constricted by an
Used in F-22 Raptor and B2 stealth bomber
Source: http://images01.military.com/media/equipment/military-aircraft/f-22-raptor/f-22-raptor_009-ts600.jpg
Answer via Moodle ! How do they work ?
AE-705 Introduction to Flight Lecture-06 Capsule-03
NESLIE (2009)
DANIELA (2011)
Verbeek, M. J., and H. W. Jentink. "Optical air data system flight testing. NLR-TP-2012-068, 2012
AE-705 Introduction to Flight Lecture-06 Capsule-03
AE-705 Introduction to Flight Lecture-06 Capsule-03