| General Information | |
|---|---|
| Type | Stal-7 (Сталь-7) |
| Function | Passenger |
| Year | 1936 |
| Crew | 2 |
| Powerplant (2) | |
| Type | M-100 (M-103) |
| Power | 760hp (860hp) |
| Size (m) | |
| Length | 16 |
| Height | 4.89 |
| Wingspan | 23 |
| Wing area (m2) | 72 |
| Weights (kg) and loads | |
| Empty | 4800 |
| Normal | 7200 |
| Maximum | 11000 |
| Wing Load (kg/m2) | 100 (153) |
| Power load (kg/hp) | ~4.5 |
| Speed (km/h) | |
| at 0m | 417 |
| at 3000m | 450 |
| Cruising | 412 |
| Landing | 90 |
| Range (km) | |
| Practical | 5000 |
| Endurance | 13h |
| Ceiling (m) | |
| Practical | 10000 |
| One engine | 4500 |
| Payload (kg) | |
| Fuel | up to 6000 |
| Cargo (max) | 5600 |
| Cabin size LxWxH | ?m3 |
| Seats | 12 |
Stal-7 (Сталь-7) by R.L.Bartini
;)
|
In the mid-30's many Soviet design teams payed attention to new class of passenger aircraft - high-speed twin-engine machines for 10 to 20 passengers. Certainly, conversion into a bomber was often among designer's goals. R.L.Bartini at NII GVF joined the effort in 1933. He took aim on the record speed - 400km/h. His project was approved in July 1934, and in Fall 1936 new aircraft rolled out from ZOK NII GVF.
Wing of the Stal-7 had unusually sharp gull-shape and strong tapering (factor 4). Landing gear and the engines were fitted at the wing bend. Such a solution resulted in sharp drag reduction with engines running ("effect Bartini").
Original fuselage design was similar to one used on light aircraft of A.S.Yakovlev - steel load carrying frame with light "secondary" frame carrying fabric skin. But this fuselage was found not sufficiently rigid thanks to the... bomb bay hidden in the floor. All-aluminum monocoque was used instead.
2-spar wing had a wielded frame structure and special airfoil developed by R.L.Bartini himself. Each wing consisted of 200 steel tubes of various diameters. Joints were reinforced by thicker insets of softer steel tubes. Engine cradle was integrated into the wing structure.
Construction was labour intensive and demanding to the wielding quality. ZOK NII GVF team had sufficient experience in wielding (see DAR page), and no wing failures were experienced. Same construction of the wing (but with aluminum skin) was used later in the bomber development, also with success. Attempt to use traditional rolled profiles for the wing spars was made, but proved superiority of an original design.
Trials (Winter 1936 - 1937) were successful, and in Spring 1937 Stal-7 was chosen for record round-the-world flight. Aircraft was fitted with 27 internal fuel tanks (7400l) and upgraded navigational equipment. Stal-7 was under additional trials, when R.L.Bartini was imprisoned as a "Mussolini's spy". Since January 1938 he did not participate in Stal-7 development for some time... But Z.B.Tsentsiper, N.V.Sinelschikov, M.V.Orlov, V.G.Yermolaev et al finished the modification. Crew of pilot N.P.Shebanov, co-pilot V.A.Matveev and engineer radio-operator N.I.Baikuzov performed two non-stop flights in 1938:
August 28 : Moscow - Simferopol - Moscow, 2360km in 8hours
October 6 : Moscow - Batumi - Moscow, 3800km in 11hours
In January 1939 this crew and designers (without "enemy of the people" R.L.Bartini) were invited to special meeting (Kremlin?) where they presented a detailed report about Stal-7. Question of a bomber conversion was raised. Designers promised to have a preliminary project in 2...3 months (indeed, it was almost ready from the beginning). On the same meeting a 5000km non-stop fight for the Word Record was approved.
This flight took place on August 28 1939. 5038km route Moscow - Sverdlovsk - Sevastopol - Moscow was covered in 12hours 30min 56sec, and the World Record was set. Round-the-World tour was terminated by the outbreak of World War II.
