CC BY
8Impact Factor: SJIF 2019 - 5.11 TE^HHK^ ^YKH
2020 - 5.497
2021 - 5.81
THE PRICIPLE OF OPERATION OF THE DEVICE THAT MEASURES THE VERTICAL
FLIGHT SPEED OF THE AIRCRAFT
MURAD ASHRAFOV
Azerbaijan state university of petroleum and industry
Abstract: A device that gauges the rate of change in altitude in an aircraft is called a vertical speed indicator (VSI), also known as a rate of climb and descent indicator (RCDI). It is one of the basic flight instruments that assists the pilot in maintaining a desired altitude or vertical speed during flight. This article explains the principle of operation of the VSI based on the pitot-static system, and discusses its limitations and errors.
Key words: vertical speed indicator, VSI, aircraft, pressure, calibrated leak
INTRODUCTiON
An aircraft's rate of climb or descent, measured in feet per minute or meters per second, is shown by the VSI instrument. The VSI is based on the pitot-static system, which consists of a pitot tube and a static port that measure the total pressure and the static pressure of the air, respectively. The static and dynamic pressures as a result of airspeed are added to create the total pressure. The square of airspeed is inversely related to the relationship between static and total pressure. The VSI employs a diaphragm, which is a flexible membrane that expands and contracts with changes in pressure. The diaphragm is connected to a calibrated leak, which is a small hole that allows air to flow in or out at a constant rate. The diaphragm is also connected to a needle, which moves along a circular scale or a ribbon to indicate the vertical speed.
Diaphragm
Calibrated Direct Static
Leak Pressure
Figure 1. An illustration of a vertical speed indication Principle of Operation.
Following are some possible explanations on how the VSI works:
• When the aircraft is on the ground or at a constant altitude, the pressure inside and outside the diaphragm is equal and there is no air flow through the calibrated leak. On the scale or ribbon, the needle is pointing to zero.
• Because of the calibrated leak, the static pressure outside drops during ascent of the aircraft more quickly than the pressure inside the diaphragm. This creates a positive pressure difference that causes the diaphragm to expand and push the needle upward on the scale or ribbon. The magnitude of the needle deflection is proportional to the rate of climb.
• As the plane descends, the calibrated leak causes the static pressure outside to rise more quickly than the pressure inside the diaphragm. This creates a negative pressure difference that causes
ОФ "Международный научно-исследовательский центр "Endless Light in Science"
Impact Factor: SJIF 2019 - 5.11 TE^HHK^ ^YKH
2020 - 5.497
2021 - 5.81
the diaphragm to contract and pull the needle downward on the scale or ribbon. The magnitude of the needle deflection is proportional to the rate of descent.
Figure 2 - A vertical speed indicator showing positive and negative rates
Limitations and Errors.
The VSI has some limitations and errors that need to be considered by pilots:
• The VSI has a lag, which means that it takes some time for it to respond to changes in vertical speed. This is due to the inertia of the diaphragm and the air flow through the calibrated leak. The lag can be reduced by using a smaller diaphragm and a larger calibrated leak, but this also reduces the sensitivity and accuracy of the instrument.
• The VSI can be affected by pitot-static errors, which are errors caused by variations in airflow around the pitot tube and static port due to changes in airspeed, angle of attack, sideslip, turbulence, icing, etc. These errors can cause incorrect readings of vertical speed that do not reflect reality.
• The VSI can also be affected by instrument errors, which are errors caused by defects or malfunctions in the instrument itself, such as leaks, misalignment, calibration errors, etc. These errors can cause inaccurate or erratic readings of vertical speed that need to be corrected or ignored.
CONCLUSION
The VSI is an essential device that measures the vertical flight speed of the aircraft based on the pitot-static system. It enables the pilot to control the altitude and vertical speed during flight. However, the VSI also has some limitations and errors that need to be taken into account by the pilot for safe and efficient flight operations.
REFERENCES:
1. Vertical Speed Indicator | SKYbrary Aviation Safety https://skybrary.aero/articles/vertical-speed-indicator
2. Davlyatchin R.R. Influence of a radiant heating system on the heat-insulating properties of coating of industrial buildings and structures: dissertation of Cand. tech. Sciences-Tyumen: 2009 - 117 p.
3. Aerodynamic, Megep, Turkish Ministry of Education, Ankara, 2011, 48 p.
4. Andreas Kampf. Energie- und physiologische Untersuchungen zur Verwendung von Gasinfrarotstrahlern bei der Beheizung grober Räume im Vergleich zu anderen Heizsystemen. Die Ruhr-Universität Bochum hat eine Dissertation verfasst, um den Doktortitel als Ingenieur zu erhalten. - Bochum: 1994- 196 s.
5. Flight instruments - Wikipedia https://en.wikipedia.org/wiki/Flight_instruments
6. File:Vertical speed indicator.svg - Wikimedia Commons https://commons.wikimedia.org/wiki/File:Vertical speed indicator.svg Chapter 7
ОФ "Международный научно-исследовательский центр "Endless Light in Science"
