In the era of science and technology, many electronic devices are pursuing smaller volume and lighter weight. This goal has also been applied to aircraft research and development. Today, let's talk about the world's smallest fighter - xf-85. This is a parasitic fighter, that is, the way to use large aircraft to carry small aircraft to make up for the lack of range or perform specific tasks of the latter, also known as "sub carrier aircraft". This pocket fighter looks like an egg and is called "flying egg". Its test flight time is very short, which can be described as a flash in the pan, but its emergence is a bold exploration in the field of fighter design. During the Second World War, it became normal for long-range bombers to go deep into the enemy's rear to perform tasks alone. Due to the short range of escort fighters, pilots often had no return. In order to solve the problem of long-range bomber escort, the U.S. military put forward the idea that there should be escort fighters around the bomber, and specially commissioned McDonald aircraft company to develop a parasitic fighter. McDonald's quickly came up with a plan for fighter planes to be half buried in the belly of bombers, but it was not approved. After that, the scheme was modified to install the sub aircraft into the master aircraft, put it in when it needs to fight and take it back after it is over, so as to solve the problem that the long-range bomber has no fighter escort. In 1946, two xf-85 prototypes came out one after another. It uses a 37 degree swept back main wing that can be folded upward. The fuselage is 4.53 meters long, the wingspan is 6.43 meters, and the height is 3.35 meters. It is several times smaller than a modern fighter. The size of the whole aircraft is similar to that of a small car. Instead of the traditional landing gear, a hook rod which can be incorporated into the fuselage is installed at the nose of the aircraft for lifting and recycling. Although the body is small, the empty weight of the xf-85 is 1807 kg and 2540 kg when fully armed. The engine adopts a turbojet engine with a thrust of 1360kg, and the maximum flight speed at an altitude of 10000 meters can reach 922km per hour. However, its flight time is only about 30 minutes. It is an "egg" with wings but not far away. The first xf-85 prototype was damaged during wind tunnel test, so only the second prototype can be used for flight test. On August 23, 1948, the xf-85 was carried by the eb-29 master aircraft and flew to an altitude of 6096 meters, but it was not launched. On August 28, the first free flight was launched. An ace test pilot piloted the xf-85 away from the eb-29 aircraft and flew freely for 15 minutes to test the controllability of the new aircraft. The xf-85 had a problem when returning to the mother plane. Due to the strong turbulence, it was difficult to maintain relative stability. The test pilot couldn't hook the hanger several times, and finally had to choose to make a forced landing on a dry lake bed. Soon, the adjusted xf-85 flew into the blue sky again. This time, in a fearful atmosphere, it finally successfully docked with the mother aircraft, and the subsequent two test flights completed the recovery procedure without danger. However, in the fifth test flight, the base rectifier of the nose hook was blown off by violent air flow, resulting in the xf-85 almost out of control. The test pilot had to make a forced landing by means of belly landing. Fortunately, the body was too hard and did not disintegrate. Learning from this lesson, xf-85 temporarily installed an external landing gear to solve the problem of airport forced landing. In order to improve the handling stability, the designer added a vertical stabilizer on the wing tip, which had little effect. The docking of the sixth test flight failed again. Finally, they analyzed and found that due to the poor aerodynamic layout of xf-85, the irregular airflow generated around the master aircraft has a great impact on it during flight. Therefore, it is difficult for even the ace test pilot to hang the hook on the hanger during the air test flight. In addition, the performance of xf-85 is not as good as that of interceptors to be put into service abroad. In the autumn of 1949, the US Congress cut the budget, resulting in a shortage of funds for several US Air Force projects, so the US Air Force terminated the xf-85 project on October 24, 1949. Fortunately, both xf-85 prototypes have been retained and placed in the museum for people to visit. (outlook new era)