Mo Ta-Yen served in the 17th PS.

In April 1938 Mo Ta-Yen served in a 3rd PG detachment equipped with Polikarpov I-15bis.

On 29 April 1938 (Japanese Emperor Hirohito’s birthday) 18 G3M2s of the 13th Kokutai Japanese Naval Air Force (IJNAF) escorted by 27 A5Ms of the 12th Kokutai under the command of Lieutenant Commodore Y. Ozono attacked Wuhan.
The 4th PG at Hankow Field had nine I-15bis, seven I-16s, and two I-16s from the 24th PS. The Russian volunteers had 23 I-15bis and 16 I-16s. The 3rd Group detachment based at Hsiao Kan was equipped with four I-15bis and six I-15bis were from the 17th PS, 5th PG.
Reconnaissance revealed the Japanese intentions in good time and early in the morning at Nanchang’s aerodromes (there were two) the order went out to all to fly to Hankow in flights, at treetop level (altitude no greater than 25 m). By 08:00 a lot of fighters had concentrated there. By 09:00 all the aircraft had been re-fuelled and the pilots were in the cockpits waiting the order to take off. That day dense clouds at several levels covered the sky, beginning at 2000-2500 m.
The first communications from the air warning system (VNOS) began to be received at 10:00. At 14:00, when the Japanese aircraft approached Wuhan fighters were already waiting in the air with sufficient altitude. According the previously drawn up plans, the I-15bis closed in on the Japanese fighters in a pincer attack while the I-16 formation fell upon the bombers.
Mao Ying-Chu, commander of the 4th PG, led nine I-15bis into the battle. Liu Chi-Han and Liu Chung-Wu took off first and met over a reported 20 Japanese aircraft. They each claimed a Japanese aircraft, as did Yang Shen-Yen. Moments later Liu Chung-Wu claimed a second Japanese aircraft. His aircraft was, however, also damaged in this battle.
Teng Ming-Teh led the I-16s of the 4th PG and 24th PS to patrol the airspace over the airfield. The Russians at first left the formation, but then turned around and joined in the battle near Liang Tze Lake. They claimed six Japanese bombers and seven fighters.
During the combat Lieutenant Chen Huai-Min of the 23rd PS claimed a Japanese plane. His plane was then badly damaged and he rammed another Japanese aircraft and both aircraft exploded in mid-air. Chen was killed.
While the combat was in full swing the four I-15bis of 3rd PG and the six I-15bis of 17th PS arrived overhead at 6500 feet south of Wuhan after that the Japanese bombers had dropped their bombs. They immediately joined combat and Shen Tse-Liu, commander of the 3rd PG detachment severely damaged one Japanese bomber. His vice-commander Li Chia-Hsun and Mo Ta-Yen each downed a Japanese bomber. Zhu Jia-Xun flew the fourth 3rd PG I-15bis. During the combat Zhu claimed to have downed one of the G3M2s south-east of Wuchang. This was near the position where two of the IJNAF G3M2s was downed. Many other Chinese and Russian volunteer pilots also made claims so Zhu should probably only be credited with a "shared" kill.
The Russian volunteer Aleksey Dushin told in his memoirs that they took of early, first Aleksey Blagoveshchenskiy, after him the entire group in established order. The I-15bis were to join battle with the fighters. At a height of about 3000m they moved off from Hankow about 100 km in the direction of Nanking, orienting themselves through the gaps in the clouds by the channel of the Yangtze. Not finding the fighters, on a return course, through gaps in the clouds they discovered a large group of bombers approaching on a parallel course. With a sudden attack at close range they right away set fire to three of the bombers, including the formation leader. The formation immediately fell apart and jettisoned its bombs in a rice paddy. In the air, developed dogfights and in various parts of the sky appeared the torches of burning Japanese aircraft. The “Chizhi” chased after the bombers for their full radius of action - more than 200 km. When his ammunition was completely exhausted Dushin ran into two A5Ms but there was nothing he could do to them. A. S. Zingaev’s group, with an advantageous position attacked a group of Japanese bombers on the approaches to the aerodrome, and in their first attack shot down two (Zingaev shot down the leader). In this combat Grigoriy Kravchenko shot down two (one bomber and one A5M) aircraft. But in the end, he was cut off from his formation and hard pressed by four Japanese who set his aircraft afire. He was saved by Anton Gubenko, who came to his help at the right moment.
Known Russian volunteers known to have claimed in this combat are Blagoveshchenskiy, Dushin, A. Grisenko, Gubenko, Kravchenko (two), I. Puntus, Georgiy Zakharov and A. Zingaev. The major success of the volunteers was explained by the Japanese fighters, which were late at the rendezvous with their bombers, and also by the Soviets’ successful use of the clouds.
AA at Wuchang also fired at the Japanese aircraft over Hanyang and claimed two of them.
A total of 21 Japanese aircraft, 11 fighters and 10 bombers, were claimed shot down in this fierce 30-minute battle and 50 aircrew were killed. Two parachuted and were captured. However, it has only been possible to verify two lost G3M2s.
Twelve aircraft of the Chinese and Soviet volunteers were lost and five pilots killed; identified are Chen Huai-Min, starshiy leytenant Lev Zakharovich Shuster (born 1914) and kapitan Aleksey Yevgen’yevich Uspenskiy (born 1906). Shuster was reportedly killed while colliding with a Japanese aircraft.
The Japanese reported that when their formation appeared over Hankow, a reported 78 I-15s and I-16s rose to intercept. They claimed that in a 30-minute battle they destroyed no fewer than 40 Chinese aircraft while themselves losing only two A5Ms (PO2c Ken-ichi Takahasi (Pilot 19) and PO3c Kinji Fujiwara (Pilot 29) being killed) and two G3M2s. During this combat Motonari Suho claimed his first victory (totally 15 victories – 11 in China) but his own aircraft received hits, however; on the way, back to base he had to make an emergency landing at Anking because he ran out of fuel. Lieutenant Takahide Aioi claimed his first two victories when he shot down two I-15s (totally 10 victories – 5 in China). The Japanese attribute the greatest part of their success to the inexperience of their opponents. In other accounts (also based on Japanese sources), 67 Soviet aircraft participated in the battle, of 19 I-15bis and six I-16s were flown by Soviet volunteers. According to these accounts the Chinese lost nine aircraft and four pilots.
After this fierce combat Japanese did not attack Wuhan for a month.

Mo Ta-Yen ended the war with 1 biplane victory.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1938
1	29/04/38	14:00-	1	Enemy bomber (a)	Destroyed	I-15bis		Wuhan area	17th PG

Biplane victories: 1 destroyed.
TOTAL: 1 destroyed.
(a) Claimed in combat with G3M2s of the 13th Kokutai and A5Ms of the 12th Kokutai of the Japanese Naval Air Force. Chinese pilots and Russian voluntary pilots claimed 21 Japanese aircraft, 11 fighters and 10 bombers, but it seems that only two G3M2s and two A5Ms were admitted. The Japanese claimed 40 Chinese aircraft but only twelve aircraft of the Chinese and Soviet volunteers were lost and five pilots killed.

Sources:
Japanese Naval Aces and Fighter Units in World War II - Ikuhiko Hata and Yasuho Izawa, translated by Don Cyril Gorham, 1989 United States Naval Institute, Annapolis, ISBN 0-87021-315-6
Soviet Fighters in the sky of China, Part II - Anatolii Demin, 2000 Aviatsiia Kosmonavtika 10 (translated by George M. Mellinger)
Additional information kindly provided by Raymond Cheung and Tom Chan, Andrei Demjanko and Mirek Wawrzyński.