Question:  Jagdgeschwader 52 included the fighter ace who joined the Luftwaffe in what year?

Context paragraphs:
Kurt Welter: Kurt Welter (25 February 1916 – 7 March 1949) was a German "Luftwaffe" fighter ace and the most successful "Jet Expert" of World War II.  A flying ace or fighter ace is a military aviator credited with shooting down five or more enemy aircraft during aerial combat.  He claimed a total of 63 aerial victories—that is, 63 aerial combat encounters resulting in the destruction of the enemy aircraft—achieved in 93 combat missions.  He recorded 56 victories at night, including 33 Mosquitos, and scored more aerial victories from a jet fighter aircraft than anyone else in World War II and possibly in aviation history.  However this score is a matter of controversy; research of Royal Air Force losses suggests Welter overclaimed Mosquito victories considerably.

Böblingen Airport: Böblingen Airport (German: "Flughafen Böblingen" ) (IATA: PHM) was built in the mid-1920s for the city of Stuttgart in Germany.  Bordered by Calwer Straße (K1073) and the E41, it lies northwest of Böblingen and south of the Daimler factory in Sindelfingen.  An aircraft industry developed around this airfield, which was used by the military during the Second World War.  On September 1, 1939 the airbase was the home station for the I/JG 52 (1st Group of Jagdgeschwader 52) which was flying the Bf109 E-1 fighter aircraft.  On that day its strength was 39 aircraft.

Jagdgeschwader 52: "Jagdgeschwader" 52 (JG 52) (52nd Fighter Wing) of the Luftwaffe, was the most successful fighter-wing of all time, with a claimed total of more than 10,000 victories over enemy aircraft during World War II.  It was the unit of the top three scoring flying aces of all time, Erich Hartmann, Gerhard Barkhorn and Günther Rall.  The unit flew exclusively with the various versions of the Messerschmitt Bf 109 throughout the war.

Hans Beißwenger: Hans Beißwenger (8 November 1916 – 6 March 1943) was a German Luftwaffe fighter ace and recipient of the Knight's Cross of the Iron Cross with Oak Leaves during World War II.  A flying ace or fighter ace is a military aviator credited with shooting down five or more enemy aircraft during aerial combat.  In 500 combat missions, Beißwenger was credited with 152 victories, making him the 34th highest-scoring Luftwaffe fighter pilot of World War II.  He was "ace-in-a-day" twice, shooting down five aircraft on a single day.  He claimed all but one of his victories over the Eastern Front.  He was reported missing in action in March 1943.

Hubertus von Bonin: Hubertus von Bonin (born 3 August 1911, Potsdam – 15 December 1943) was a German Second World War fighter ace who served in the "Luftwaffe".  A flying or fighter ace is a military aviator credited with shooting down five or more enemy aircraft during aerial combat.  Bonin is credited with shooting down 77 enemy aircraft.  The majority of his victories were claimed over the Eastern Front.  He also claimed four victories in Spain during the civil war.  His commands included "Geschwaderkommodore" of Jagdgeschwader 54 (JG 54—54th Fighter Wing).

Gerhard Barkhorn: Gerhard "Gerd" Barkhorn (20 March 1919 – 8 January 1983) was the second most successful fighter ace of all time after fellow "Luftwaffe" pilot Erich Hartmann, the two people to ever exceed 300 confirmed victories.  Barkhorn joined the "Luftwaffe" in 1937 and completed his training in 1939.

Friedrich Beckh: Friedrich Beckh (17 January 1908 – 21 June 1942) was 48 victory-Luftwaffe flying ace and recipient of the Knight's Cross of the Iron Cross.  The Knight's Cross of the Iron Cross was awarded to recognise extreme battlefield bravery or successful military leadership.  He held the position of Geschwaderkommodore of fighter wing Jagdgeschwader 51 and Jagdgeschwader 52.

13 JG 52: 13.  Staffel (slowakisches) Jagdgeschwader 52 (13. (slovak)/ JG 52) was a front-line unit of the Nazi Germany's Luftwaffe made up of Slovak personnel during World War II.

Heinrich Sturm: He joined 6. /Jagdgeschwader 52 (JG 52—6th squadron of the 52nd fighter wing) with the rank of "Feldwebel" (Sergeant) in the summer of 1941, he claimed his first three aerial victories at the end of the year.

Friedrich Wachowiak: Friedrich Wachowiak (13 February 1920 – 16 July 1944) was a former German Luftwaffe fighter ace and recipient of the Knight's Cross of the Iron Cross during World War II.  The Knight's Cross of the Iron Cross was awarded to recognise extreme battlefield bravery or successful military leadership.  Wachowiak served with Jagdgeschwader 52 (JG 52—52nd Fighter Wing) and Jagdgeschwader 3 (JG 3—3rd Fighter Wing) and gained his first victories against the Royal Air Force in 1940.  At the end of 1941 he received his 20th victory and the 40th was in March 1942.  His first Soviet victory was on 1 May 1942.  On 7 May 1942 he reported his 62nd and on 29 November 1942 the 86th victory.  1943/1944 he was temporary a fighter flight trainer and came back to the front in May 1944 with the JG 52 over Normandy.

Supporting paragraphs: Jagdgeschwader 52 Gerhard Barkhorn
Answer: 1937