The Do 217 H was a conversion of a Do 217E with DB 601 engines fitted with experimental turbo-superchargers. The H V1 to H V3 prototypes were designed as unarmed bombers with DB engines with 3.8 m VDM propellers. Bombs, Recon cameras, and dive brakes were all dispensable. The H V1 was delivered in September 1941 but crashed soon after as a result of propeller failure . After the evaluation of the flight, the wings were expanded to 67m². In September 1943, after nearly two years of constant delays, the H V1 was fitted with DB603G prototype engines. It is unknown how these tests developed. The H V2 also crashed on 25 October 1942, severely injuring the crew. The cause was the propellers. The H V3 tested a variety of DB603s until November 1944. On 9 June 1942 it successfully tested at high altitude. It also proved successful testing twin exhausts and pulse jets. Later, in October three and four-bladed duralumin propellers were used. Because of better vibration characteristics, the four-bladed VDM was judged the best performer. On 11 October 1942 the first flight was made at 8,000 m. After, 9,000 m flights were reached. In September 1943 the DB603E had improved superchargers, giving better high-altitude performance. The H series continued as test beds for the M series until October, when they were cancelled for lack of fuel.

Sources:
Gunston, Bill - The Encyclodepia of the Worlds Combat aircraft, 1976, Chartwell Books, Inc., New York
Brown, Eric, Captain - Wings of the Luftwaffe, 1979, Airlife Publishing Ltd., Shrewsbury
Gunston, Bill & Wood, Tony - Hitler's Luftwaffe, 1977, Salamander Books Ltd., London
Donald, David - The Complete Encyclopedia Of World Aircraft, 1997, Brown Packaging Books Ltd., London
Wikipedia - Dornier Do 217