Fixed Wing
This question is one I researched some time ago and the best answer I could come up with was a Notam back in the early days issuing a decree. The Vimy and 0/400 of WWI had the pilot on the right and the left occupied by an observer or gunner. The story,
LONDON-PARIS MACHINES COLLIDE
On Friday of last week (7 April 1922) an extremely regrettable and most unusual accident marred the running of the London Continental Air Service, which has hitherto been remarkably free from serious disasters. It is an accident, also, all the more unfortunate in that it involved the recently inaugurated Daimler Hire Service. A Goliath belonging to Grands Express—F-GEAD—piloted by M. Mire and carrying a mechanic and three passengers had left Le Bourget at 12.6 p.m. for Croydon. The weather was very misty and visibility bad, and when flying over Thieuloy, near Grandvilliers, at a height of only a few hundred feet, a D.H. 18, from Croydon—G-EAWO—of the Daimler Service, piloted by R. E. Duke and carrying a boy steward and mails, suddenly loomed out of the mist. Before either pilot could turn, the machines collided, and then crashed to earth in flames. The D.H. 18, it is stated, had its wing and tail broken off by the impact and fell immediately, whilst the Goliath swooped to earth a little further off. Assistance was at once rushed to the wrecked machines, but with the exception of the boy steward —Hesterman—who was terribly injured, all were found to be dead. The boy was taken immediately to the village, but died from his injuries some time later.
R. E. Duke was a well-known pilot of the Continental services, and had a distinguished war record in the R.A.F. He was formerly, before joining the Daimler service, with the Aircraft Transport and Travel Co. and the Royal Dutch Aviation Co. M. Mire, the French pilot, was also well known as a Continental Air Service pilot, and had been flying for Grands Express for over a year.
The following message of condolence has been sent by the Secretary of State for Air to M. Laurent Eynac, French Under-Secretary of State for Air, and to the Chairman of Daimler Hire, Ltd. :—
In my own name and that of the Air Council I offer you my deep sympathy on the fatal air collision which occurred yesterday, the only accident of this kind in the history of air transport between Great Britain and France.
(Signed) FREDERICK GUEST,
Secretary of State for Air.
NOTICE TO AIRMENRules for Flight over Air Routes.
It is notified :
1. In order to give general application to the rules designed to minimise the risk of collision, which have hitherto only applied to aircraft flying over an officially recognised air route, the following rules have been agreed on by the British, Belgian and Dutch Governments :—
(a) The normal procedure in order to reduce the risk of collision to the minimum consists in flying in a straight line, steering by the compass and carefully watching the air space in the region ahead of the aircraft. Every pilot, when flying on a compass course, shall, whenever it is safe and practicable, fly on the right of the straight line joining the point of departure to the point of arrival.
(b) When an aircraft is flying beneath cloud, it must keep at a fair distance below the cloud base in order to see and be seen.
(c) When a pilot decides to follow a route which is officially recognised or consists of a line of ground marks such as a road, railway, canal, river, etc., he should bear in mind that the risk of collision with another aircraft following the same route is considerable.
Every pilot following such a route, therefore, shall endeavour to keep it at least 300 metres on his left. (My bolding)
(d) Every pilot who decides to cross any route he is following shall cross it at right angles and as high as circumstances permit. Should he desire, after crossing it, to resume flight in a direction parallel to the route, but keeping it on his right, he must keep sufficiently far from it to avoid aircraft following it in the normal way.
N.B.—These regulations shall in no way relieve pilots from the necessity of conforming to the regulations set forth in Annex D of the International Air Convention of October 13, 1919.
2. Pilots are not obliged by the above rules to follow an officially recognised air route, where such exists. " Point of arrival " and "point of departure" in rule (a) include all turning points on routes which are normally not flown on one straight course. The straight line referred to is that joining the extremities of each section of the route which is flown on one course.
3. Certain portions of the following routes have been officially recognised by the authorities concerned :—
London—Paris
London—Brussels
Paris—Brussels
London—Rotterdam
Amsterdam—Berlin
Rotterdam—Berlin
Rotterdam—Brussels.
4. Instances have recently occurred in which pilots have been careless in the observance of the rules which have been expressly designed for the general safety of all aircraft.
5. The importance of rigidly adhering to these regulations cannot be too strongly accentuated, and all pilots are invited to report at once to the Secretary, Air Ministry (D.C.A.), any infringements which may come to their notice.
And you thought SLOP was a new concept.
Helicopter
Helo convention does have the captain sitting on the right but there are exceptions, the Bell 47, also Enstrom and I think Hughes 500. The mission at times dictates the side the captain sits. In the S-76 normally the captain sits on the right, but in the SAR role with one operator, the captain sits on the left. Ditto long lining, captain sits on the left. In Vietnam on the Huey slick the US Army convention was for the captain to sit in the left seat. The reason given to me was that the visibility was much better because that seat had a smaller instrument panel obscuring the view. Personally when I made captain I stayed in the right seat because of the ease of access to radios.
Why helo guys sit on the right has always been a subject of much discussion and there are many thoughts but little concrete. The best theory I have come across and think probable is that the first helos had the one and only collective lever mounted between the two seats. That meant the left seat guy flew with left hand on the cyclic and right hand on the collective, the right seat guy of course it was the reverse, vis right hand cyclic, left hand collective. It was said that Igor preferred to sit in the left seat when training the new boys, and so the new pilots (in the right seat) grew accustomed and naturally preferred that position when they were let loose to the squadrons. Hey presto, a convention is born. A photo does exist of Igor occupying the left seat whist the aircraft is being flown by another pilot.
Photos show the Sikorsky R-4 (the first mass produced helo and the first to enter service with the United States Army Air Forces, Navy, Coast Guard, Royal Air Force and Royal Navy) doing ship trials being flown solo from the left seat. Other photos show the helo with a hoist on the left side, which meant the helo had to be flown from the right seat for the hoistee occupied the left seat once up at the door (Lateral C of G considerations aside). So maybe Sikorsky either set a convention by deciding on what side to put the hoist, or the side to put the hoist was dictated by the preference of seating position by the majority of pilots. Who knows?