Gavrikov-Glagolev-Stepanov GGS-33

The **GGS-33** was a twin-engine Soviet airliner developed in the 1930s. It flew for Aeroflot reliably until 1951, when Aeroflot retired its last GGS-33. Only 65 GGS-33s were built, including the prototype.

## Development

A small team of designers consisting of Mstislav Demid Gavrikov, Mitrofan Nikifor Glagolev, and Miron Timofei Stepanov began work in January 1935 to meet requirements for an airliner from Aeroflot. By September, they had built a prototype. Flight testing began in November 1935, with test pilot Gennadiy Petrov at the controls. Petrov performed the maiden flight on the 7th of November. Conclusions of the test flights revealed that the main problems were: engine cooling was inadequate, and the brakes were not powerful enough.

After a month of correcting these issues, further flight testing began. Albeit for a few stability issues, the GGS-33 performed well, with the test pilot praising its maneuverability. By January 1936, the designers had fixed the problems, and Aeroflot received the prototype as a gift. Aeroflot placed an order for 49 GGS-33s, and by April 1937, the Kharkiv Aircraft Factory delivered all GGS-33s to Aeroflot on time.

In March 1937, the **GGS-33A**, a version of the GGS-33, went into production. The GGS-33A featured more powerful ASh-62 engines, each producing 850 hp. Aeroflot placed a production order for 15 GGS-33As, and by February 1938, Aeroflot received all GGS-33AS.

### Design

The GGS-33 was of mainly all-metal, monocoque construction. The fuselage used steel. Inside the fuselage was space for ten passengers and three pilots, including a captain, a first officer, and a flight mechanic. However, the latter was optional. A small cargo compartment was present, capable of carrying 280 kg of cargo. The GGS-33 featured a streamlined fuselage for better aerodynamics. The tail section used a conventional tail design, with fabric covering the control surfaces to save weight. A trim system was also present on the aircraft.

Two nine-cylinder, air-cooled Shvetsov M-25 radial engines, an engine liked for its durability, fuel economy, and power-to-weight ratio, powered the aircraft. The design featured retractable landing gears of conventional design that retracted rearwards into the engine nacelles. The wings also featured plain flaps used to aid takeoff and landing.

In the GGS-33A variant, two nine-cylinder, supercharged, air-cooled Shvetsov ASh-62 radial engines powered the aircraft.

## Operational history

The GGS-33 would go on to serve Aeroflot reliably. It flew these routes:

* Kharkiv – Kyiv
* Moscow – Leningrad
* Moscow – Minsk
* Moscow – Stalingrad

Soviet pilots liked the GGS-33 because of its stability and maneuverability. According to some Soviet pilots, the aircraft had unintentionally performed barrel rolls. Passengers of the GGS-33 liked its roominess but disliked its noisy engines.

Various GGS-33s remained in service with Aeroflot until as late as 1951, when Aeroflot retired them. Accidents and incidents caused the loss of five GGS-33s in their operating time, but its safety records remained good.

The five hull losses the GGS-33 encountered were primarily pilot errors. Three of these accidents included controlled flight into terrain and runway excursions. An engine failure caused the other two.

## Operators

**Soviet Union**

* Aeroflot

## Specification (GGS-33)

**General characteristics**

* **Crew:** two-three
* **Capacity:** ten passengers and 280 kg of cargo
* **Length:** 18 m
* **Wingspan:** 25.95 m
* **Height:** 4.79 m
* **Wing area:** 87.9 m²
* **Empty weight**: 5,419 kg
* **Gross weight:** 8,911 kg
* **Powerplant:** 2 × Shvetsov M-25 nine-cylinder, air-cooled radial engines, 750 hp each
* **Propellers:** 3-bladed constant-speed metal propellers

**Performance**

* **Maximum speed:** 325 km/h
* **Cruise speed:** 290-305 km/h
* **Range:** 1,500 km
* **Service ceiling:** 6,700 m
* **Wing loading:** 101 kg/m²