Rajan Wilcox
The Mikoyan-Gurevich MiG-21 is a Soviet-era fighter jet with a short range due to its limited fuel capacity. The aircraft's usable fuel capacity is 475 gallons, which is half that of the A-4M Skyhawk and a sixth of the F-14 Tomcat. The MiG-21's short endurance has been a consistent issue, with pilots finding that they could barely reach Mach 2 before running out of fuel. The Tumansky R-25 jet engine's specialty is the addition of a second fuel pump in the afterburning stage, which increases fuel consumption by 50% but provides a slight advantage in close-quarters dogfights. The MiG-21's internal fuel capacity is under 720 US gallons, with some variants carrying up to 2,600 liters (690 US gallons), but 210 gallons of this amount cannot be used due to the aircraft's center of gravity. The fuel system consists of six fuselage tanks, four integral wing tanks, and one belly drop tank, with a complex pressurization and control pressure system.
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What You'll Learn
- The Mig-21 has a usable fuel capacity of 475 gallons
- The plane's centre of gravity shifts as fuel is consumed
- Violent manoeuvres can prevent fuel from reaching the engine
- The Mig-21's engine has an emergency mode that increases fuel consumption by 50%
- The fuel system consists of six fuselage tanks, four wing tanks, and one belly drop tank
The Mig-21 has a usable fuel capacity of 475 gallons
The MiG-21 is a Soviet-designed aircraft with a usable fuel capacity of 475 gallons. The aircraft's short endurance and low fuel capacity have been noted as defects by pilots. This is partly due to the poor placement of internal fuel tanks ahead of the centre of gravity, which shifts rearward as fuel is consumed, making the plane difficult to control. This issue has been somewhat addressed by carrying fuel in external tanks closer to the centre of gravity, as well as larger external fuel tanks in Chinese and second-generation Soviet variants.
The MiG-21's fuel system consists of six fuselage tanks, four integral wing tanks, and one belly drop tank. The fuel is pressurized and transferred based on pressure levels in each tank, with the highest pressure being bled to the belly drop tank, followed by the wing tanks and then the fuselage tanks. The system includes auxiliary fuel pumps and a control pressure system to manage fuel flow.
The MiG-21's Tumansky R-25 jet engine includes a second fuel pump in the afterburning stage, which can be activated in emergency mode to increase thrust and climbing rate. However, this increases fuel consumption by 50% and has a limited operation time due to engine overheating concerns. The MiG-21's performance at high altitudes is also impacted by its modest fuel load, making it more suitable for low-level flights.
The MiG-21's fuel capacity and endurance have been a consideration in its deployment. For example, during the Israeli-Arab wars and in Vietnam, the MiG-21 was reserved for top cover duties rather than ground-attack missions. The short-range capabilities and fuel capacity of the MiG-21 have influenced its role and effectiveness in combat situations.
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The plane's centre of gravity shifts as fuel is consumed
The Mikoyan-Gurevich MiG-21 is a Soviet-designed aircraft with a short range due to its limited fuel capacity and the poor placement of its internal fuel tanks. The MiG-21's internal fuel tanks are positioned ahead of the centre of gravity, which means that as fuel is consumed, the centre of gravity shifts rearward. This shift in the centre of gravity can push the aircraft beyond its controllable parameters, making it statically unstable and difficult to control. This issue is exacerbated when the aircraft engages in violent manoeuvres, which can prevent fuel from flowing into the engine and cause it to shut down in flight.
The MiG-21's usable fuel capacity is 475 gallons, which is half that of the A-4M Skyhawk and one-sixth of the F-14 Tomcat. This limited fuel capacity results in a short endurance, with a normal pilot training flight lasting just over 30 minutes. To extend the aircraft's range, external fuel tanks can be added, but this can impact the aircraft's performance and manoeuvrability. The Chinese variants of the MiG-21 improved the internal fuel tank layout and used larger external fuel tanks to counter this issue.
The positioning of the fuel tanks in the MiG-21 is not the only factor affecting its fuel efficiency. The aircraft's powerful Tumansky R-25 jet engine, when activated in emergency mode, can increase fuel consumption by 50% over the rate in full afterburner. This increased fuel consumption gives the MiG-21 a climbing rate comparable to the F-16 in a close-quarters dogfight. However, the aircraft's overall modest fuel load and fuel system design contribute to its short range and endurance.
The MiG-21's fuel system consists of six fuselage tanks, four integral wing tanks, and one belly drop tank. The system is pressurised, with the fuel under the highest pressure being transferred first. The pressure varies from tank to tank, with the highest pressure bled to the belly drop tank, followed by the wing tanks and then the fuselage tanks. The fuel system also includes auxiliary fuel pumps to aid in the transfer of fuel to the engine. However, despite these advanced features, the MiG-21's fuel system and limited fuel capacity remain a challenge for pilots and limit the aircraft's performance.
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Violent manoeuvres can prevent fuel from reaching the engine
The Mikoyan-Gurevich MiG-21 is a fighter jet that was used extensively in the Middle Eastern conflicts of the 1960s, 1970s, and 1980s. It was also deployed in the Vietnam War and Indo-Pak conflicts. The MiG-21 has a usable fuel capacity of 475 gallons, which is half that of the A-4M Skyhawk and a sixth of the F-14 Tomcat. This limited fuel capacity was one of the most serious defects found by pilots.
The MiG-21's internal fuel tanks are located ahead of the center of gravity, which results in an unstable aircraft as the center of gravity shifts rearward when fuel is consumed. This issue is exacerbated at high altitudes, where the MiG-21 struggles to achieve its theoretical maximum speed before expending its modest fuel load.
To compensate for the limited fuel capacity and unstable design, the MiG-21 often utilized external fuel tanks positioned closer to the center of gravity. However, violent maneuvers when more than half the fuel was consumed could prevent fuel from reaching the engine, causing it to shut down in flight. This issue, inherited from the MiG-15, MiG-17, and MiG-19, was potentially catastrophic and risked tank implosions and explosions.
The MiG-21's performance was also impacted by its high wing loading, making it relatively less maneuverable than other aircraft like the MiG-17. Additionally, the MiG-21's controls are heavy, and certain emergency maneuvers require unintuitive control inputs, increasing the risk of pilot error during critical situations. These factors, combined with the aircraft's limited fuel capacity and unstable design, contributed to several accidents and losses during its operational history.
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The Mig-21's engine has an emergency mode that increases fuel consumption by 50%
The Mikoyan-Gurevich MiG-21 is a supersonic jet fighter and interceptor aircraft. It has a maximum speed of Mach 2, but pilots have reported that they could hardly reach this speed before running out of fuel. The MiG-21 has a usable fuel capacity of 475 gallons, which is half as much as the A-4M Skyhawk and one-sixth as much as an F-14 Tomcat. The range of the MiG-21 can be extended by adding external fuel tanks.
The MiG-21's internal fuel tanks are located ahead of the centre of gravity. As fuel is consumed, the centre of gravity shifts rearward, making the plane statically unstable and difficult to control. This issue was improved in Chinese variants and the second generation of Soviet variants, which had a better internal fuel tank layout and larger external fuel tanks.
The MiG-21's fuel efficiency also depends on its altitude. At higher altitudes, the aircraft can maintain higher speeds without using as much fuel as it would at lower altitudes. This is due to the thinner air at higher altitudes, which reduces drag on the aircraft. However, the MiG-21's performance at high altitudes is limited by its modest fuel load and mediocre radar range.
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The fuel system consists of six fuselage tanks, four wing tanks, and one belly drop tank
The Mikoyan-Gurevich MiG-21 is a Soviet-designed aircraft with a short range due to its limited fuel capacity. The fuel system of the MiG-21US (Type 68, NATO Mongol B) consists of six fuselage tanks, four integral wing tanks, and one belly drop tank. This configuration is similar to the MiG-21PF, MF, and BIS variants, with some differences in fuel quantity and annunciator light markings.
The MiG-21's fuel tanks are soft, made from two layers of rubber and rubberised fabric, and are located in special metal boxes between bulkheads No. 7 and No. 28. The fuel system is divided into two subsystems: the pressurization system and the control pressure system. The pressurization system utilises compressed bleed air fed to each of the eleven tanks, with varying pressures depending on the tank. The principle governing the system is that fuel under the highest pressure is transferred first.
FT-1 and FT-3 are crucial to the system's operation. FT-1 serves as a flow control unit, while FT-3 is the only tank that directly transfers fuel to the engine. FT-3 also houses two auxiliary fuel pumps. The pressure control system is directly linked to float valves that activate the fuel cock, which controls the flow of fuel.
The highest-pressure fuel is bled to the belly drop tank (BDT), making it the first tank to be consumed. Once the BDT is empty, fuel is transferred from the wing tanks (WT) to FT-3, aided by bleeding the next lowest pressure to the WTs. The fuel then flows through check valves to the fuel cock into FT-2, and then to FT-3 before being pumped to the engine. Group-3 tanks (FT-4 to FT-6) function similarly to the WTs, with an auxiliary pump assisting in fuel transfer to FT-3.
The MiG-21's fuel system includes safety features such as a network of overflow lines and pressure limiters to prevent overboosting. Additionally, the emergency jettison of the BDT can be activated pyrotechnically if needed.
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Frequently asked questions
The MiG-21 has a usable fuel capacity of 475 gallons. It has a short range and low fuel capacity, with an endurance of only 45 minutes in clean condition.
The MiG-21's fuel capacity is half that of the A-4M Skyhawk and one-sixth that of an F-14 Tomcat. It carries less fuel than a Mirage III, a Saab Draken, or a Hawker AV-8A Harrier.
The short range and low fuel capacity of the MiG-21 limited its performance. It struggled to reach its theoretical maximum Mach number at high altitudes before running out of fuel. The poor placement of the internal fuel tanks ahead of the centre of gravity also affected the aircraft's stability and controllability.
Yes, the MT and SMT variants of the MiG-21 had an increased range of 250 km (155 mi) compared to the MiG-21SM. However, this came at the cost of reduced performance in other areas, such as a lower service ceiling and slower time to altitude.
