Houston–Mount Everest flight expedition

Aerial view of Mount Everest from the south, taken in 2006.

Prior to the First World War (1914–1918), aircraft were limited to altitudes below about 10,000 feet. Technical advances in military aviation during that war, such as the invention of turbocharged and supercharged aircraft engines, allowed aircraft to reach higher altitudes. In 1918, Alexander Kellas (a British mountaineering physiologist) suggested that aircraft would soon be able to fly over Mount Everest, the highest mountain on Earth at 8,848 metres (29,029 ft), which would be useful for reconnaissance of potential climbing routes.[2] At that time, the mountain had never been climbed. In 1919, Jean Casale made the first flight to exceed the altitude of Everest, but only for a short period, and actually flying over the mountain would be far more challenging. The main limitation of high altitude flight at this time was keeping the crews alive in the low pressure and cold temperature air.

No progress on the idea was made during the 1920s, but in the early 1930s Lord Clydesdale became interested in the concept as an aviation first. Clydesdale was the youngest squadron leader in the Royal Air Force (he commanded 602 Squadron), and the son of Alfred Douglas-Hamilton, 13th Duke of Hamilton.[1][3]

No attempt could be made without substantial funding, so in September 1932 Clydesdale visited Lucy, Lady Houston at Kinrara (her estate in Scotland) to ask her to fund the expedition. The highly nationalistic Lady Houston was excited by the idea that Clydesdale put forward, feeling that flying over Everest would strengthen British rule in India (Houston was an outspoken opponent of the Indian independence movement) and impressed that Clydesdale had worn his kilt for dinner. She agreed to fund the expedition and became involved in its planning.[4]

Stewart Blacker in 1933, wearing flying gear and a monocle.

The inventor Stewart Blacker joined the expedition and assisted Clydesdale in organising it.[2] Blacker was an experienced pilot who had served in the British Indian Army from 1907 to 1932 (reaching the rank of major), so was familiar with the region. He convinced the Royal Geographical Society that a flight would provide valuable information for the planned 1933 British Mount Everest expedition, which aimed to climb to the summit. Blacker also obtained the necessary permissions from the Air Ministry, India Office and the government of Nepal to allow the flight to occur.[2]

Clydesdale decided to use two biplane aircraft for the attempt: the first Westland PV-6 (a prototype of the Westland Wallace bomber), registered G-ACBR; and a modified Westland PV-3, registered G-ACAZ (referred to as the Houston-Westland[5]). He selected David Fowler McIntyre, a flight lieutenant from 602 Squadron, to pilot the other aircraft.[1] Each pilot would be accompanied by an observer in the second seat of the aircraft: Blacker accompanied Clydesdale in the PV-3, and Sidney R. G. Bonnett, a cinematographer for Gaumont British News, accompanied McIntyre in the PV-6.[1] Bonnett was to be equipped with a Williamson Automatic Eagle III camera, with the goal of obtaining a photographic mosaic for an accurate map of the terrain.[6]

Both aircraft were modified (by Blacker)[2] to enclose the observer positions, but retained open pilot's cockpits. Oxygen systems were installed, to keep the crew alive using oxygen masks. The crews wore multiple layers of sheepskin clothing and the aircraft were modified to provide connections for heated flying suits. The supplies were sufficient for only 15 minutes at high altitude.[6]

Both aircraft were shipped from Britain to Karachi by sea, from which the crews flew them to Purnea. They took off on an open cabin flight at 8:25 am on 3 April from Lalbalu Airfield, Bihar, approximately 50 miles (80 km) south of Mount Everest[7] and returned to the same airfield three hours later.[2][8][9][10] There was too much dust in the atmosphere to obtain clear photographs, and Bonnett briefly lost consciousness due to hypoxia after damaging his oxygen line.[2] He successfully repaired the leak with a handkerchief.[8] Downward air currents induced by the mountain caused both aircraft to lose about 1,500 feet (460 m), but at 10:05 am both planes passed approximately 100 feet (30 m) over the summit.[8]

The crews made another successful flight over Everest on 19 April, when weather conditions were clearer. This time they were able to obtain photographs of the surface at specific intervals, as the planes flew over known survey locations.

The flight set milestones for developments in technology, aviation and photography.[2] The Guardian reported that "It is a splendid achievement - not for any material gains, any additions to aeronautical knowledge that it brings, for it brings few or none, but simply because it was one of the few last great spectacular flights in aviation which remained to be done."[5]

A half-hour documentary film about the flight, Wings Over Everest, won an Academy Award in 1936. It combined real footage from the expedition with staged shots of the participants (not actors).[11]

The aerial photographs were obtained too late to assist the 1933 British Mount Everest expedition, which had already reached Rongbuk Monastery – on the other side of the Himalayas from the airfield – and was ultimately unsuccessful. The photographs were made public in 1951[2] and were used by Edmund Hillary and Tenzing Norgay to plan their route to the top of Mount Everest, which they successfully climbed in 1953.[6]

• First over Everest: The Houston – Mount Everest Expedition 1933, London & Manchester: Cherry Tree (Withy Grove Press), (1938), Fellowes, P. F. M. with L. V. Stewart Blacker and P. T. Etherton and the Marquess of Douglas and Clydesdale.