Starting a radial engine
Discussion
Often when watching a radial engine being started, it is preceded by a fairly long drawn out procedure to clear oil from cylinders, particularly the lower ones, and then prime them.
Given that radial engines are used in aircraft on which the engines are pretty inaccessible for pulling through by hand, e.g. Short Sunderland, Supermarine Walrus, and in armoured vehicles which may need to start up and make a rapid departure, how do these engines get over the oil clearing/priming, and if they can, why don't the others?
I appreciate that some radials have sleeve valves whilst others have poppet valves, but both appear to be used inaccessible applications.
Given that radial engines are used in aircraft on which the engines are pretty inaccessible for pulling through by hand, e.g. Short Sunderland, Supermarine Walrus, and in armoured vehicles which may need to start up and make a rapid departure, how do these engines get over the oil clearing/priming, and if they can, why don't the others?
I appreciate that some radials have sleeve valves whilst others have poppet valves, but both appear to be used inaccessible applications.
GliderRider said:
Often when watching a radial engine being started, it is preceded by a fairly long drawn out procedure to clear oil from cylinders, particularly the lower ones, and then prime them.
Given that radial engines are used in aircraft on which the engines are pretty inaccessible for pulling through by hand, e.g. Short Sunderland, Supermarine Walrus, and in armoured vehicles which may need to start up and make a rapid departure, how do these engines get over the oil clearing/priming, and if they can, why don't the others?
I appreciate that some radials have sleeve valves whilst others have poppet valves, but both appear to be used inaccessible applications.
On the likes of the Walrus and the PBY the prop could be 'walked through' by ground crew stood on the cabin roof or rear fuselage, sometimes with the help of a rope with a loop or hood on the end which would slip over the end of the blade. Given that radial engines are used in aircraft on which the engines are pretty inaccessible for pulling through by hand, e.g. Short Sunderland, Supermarine Walrus, and in armoured vehicles which may need to start up and make a rapid departure, how do these engines get over the oil clearing/priming, and if they can, why don't the others?
I appreciate that some radials have sleeve valves whilst others have poppet valves, but both appear to be used inaccessible applications.
For the Sunderland and other flying boats with the engines in the wings I believe the engines would be serviced and prepared from tenders or pontoons if the aircraft was afloat or from portable platforms if ashore, which would put you within reach of the props to check for hydraulic lock and allow for access to the lower spark plugs/drains if excess oil was found. The Sunderland had hinged sections of the wing leading edge either side of each engine which could be flipped down to serve as platforms for mechanics to work from.
From the scanned/reproduced manuals online, it seems that the Shermans fitted with the Continental radial engine also had to be cranked by hand and checked for/cleared of oil in the lower cylinders before starting. My guess would be that if there was any prospect that the vehicle would be needed to go into action quickly the engine would be run briefly at whatever time period would be sufficient to keep the oil cleared, just as how aircraft that were on stand-by had their engines run up every now and then to keep their water and oil temperatures above the minimums for take-off. If you were really caught unawares and had to get moving, I suspect you'd just hit the button and chance it. If you bend a connecting rod, crack a head or even loosen a cylinder barrel you've got another eight and if you're in that situation that would be enough to get moving.
Some engines had shear pins or a certain level of 'slip' designed into their starter gears/clutches so that, in theory, the starter wouldn't be able to impart damaging force against a hydraulic lock. But they were always treated as lines of last resort rather than prevention systems.
Thanks 2x Chevrons! It looks as though even on tanks the first start would be a long drawn out procedure. Having done a bit more research myself I found this: Tank Radial Engine Starting Procedure See the last paragraph on Page 38 & first on Page 39. Clearly they weren't planning to have to make a quick getaway!
On the Catalina (fitted with Twin Wasps) the starter motors have a clutch on them so if an engine is hydro-locked, it won't turn over. We will motor it 14 blades before adding fuel and sparks to start (or 7 times if it's warm), same as anyone hand turning one before start which we don't do.
Source: I fly Europe's only Catalina.
Source: I fly Europe's only Catalina.
GliderRider said:
Thanks 2x Chevrons! It looks as though even on tanks the first start would be a long drawn out procedure. Having done a bit more research myself I found this: Tank Radial Engine Starting Procedure See the last paragraph on Page 38 & first on Page 39. Clearly they weren't planning to have to make a quick getaway!
If I was in a tank, I think I'd prefer one with a RR Meteor engine rather than a radial!GliderRider said:
Often when watching a radial engine being started, it is preceded by a fairly long drawn out procedure to clear oil from cylinders, particularly the lower ones, and then prime them.
Given that radial engines are used in aircraft on which the engines are pretty inaccessible for pulling through by hand, e.g. Short Sunderland, Supermarine Walrus, and in armoured vehicles which may need to start up and make a rapid departure, how do these engines get over the oil clearing/priming, and if they can, why don't the others?
I appreciate that some radials have sleeve valves whilst others have poppet valves, but both appear to be used inaccessible applications.
Martin Mars seems like it can turn them over by itself pre-start when on the water, 1 & 3 cleared here before start-up.Given that radial engines are used in aircraft on which the engines are pretty inaccessible for pulling through by hand, e.g. Short Sunderland, Supermarine Walrus, and in armoured vehicles which may need to start up and make a rapid departure, how do these engines get over the oil clearing/priming, and if they can, why don't the others?
I appreciate that some radials have sleeve valves whilst others have poppet valves, but both appear to be used inaccessible applications.
https://www.youtube.com/watch?v=e1Ij-2k3rUA
Moose. said:
On the Catalina (fitted with Twin Wasps) the starter motors have a clutch on them so if an engine is hydro-locked, it won't turn over. We will motor it 14 blades before adding fuel and sparks to start (or 7 times if it's warm), same as anyone hand turning one before start which we don't do.
Source: I fly Europe's only Catalina.
Source: I fly Europe's only Catalina.
Spent many, many strenuous sessions turning over the Yak radial by hand to clear the cylinders and prime.
The translated Soviet Yak-52 manual has a diagram showing the ground crew doing this for you and then saluting - I've showed this on a number of occasions to the Waltham donglers (youngsters getting start in aviation by working as ground-crew) and invariably had a jovial response of a salute of the two-fingered variety....
We had a modification fitted to the 52 which adds a tap to the inlet manifold which is opened when the aircraft is parked to help stop oil pooling in the lower cylinders, but it would still invariably piss oil out of the exhausts when pulling through after any time spent idle. Occasionally it required the lower spark plugs to be pulled out to drain the cylinders if there was enough resistance to pulling through - possible to bend things internally if too much force is applied. There was invariably an oil-slick on the grass when the aircraft was parked outside - there are a few choice spots on the line at Waltham closest to the clubhouse, and I remember a 172 grabbing a spot which the Yak had been parked in, and the pilot then laboriously opening the cowlings and peering into his engine trying to work out where all the oil around his nosewheel had come from.
The 52 has shear-pins on the connection from the engine to the air compressor, and a regular feature of the North Weald formation school were Yaks with no air pressure being wheeled into the maintenance facility to have them replaced, the shear-pins not reacting well (like radials in general) to the throttle being rapidly whanged about, and in the early stages of close-formation training it can tend to be a bit of a throttle whang-fest.
We had another 52 end up in a field due to a broken accessory drive shaft one year - I was part of that formation, took off as a four-ship, split into two pairs, called the other pair later for a rejoin to hear from the one still airborne that the other one had gone down, and they was going to make a low-pass to see if the occupants were OK. All ended well, they arrived back at NW by car a few hours later, clutching a few pieces of broken propeller to put behind the bar. Radials can take a relatively large amount of damage and keep going - YAKH in its time had a cylinder crack open in flight, and on another occasion had the core of a spark plug blow out and wreck some of the HT cabling, but still came home safely (I remember the crash alarm going off at Waltham for both of those) - but the in the case of the NW incident the accessory drive failure killed the mags, and that was that.
The translated Soviet Yak-52 manual has a diagram showing the ground crew doing this for you and then saluting - I've showed this on a number of occasions to the Waltham donglers (youngsters getting start in aviation by working as ground-crew) and invariably had a jovial response of a salute of the two-fingered variety....
We had a modification fitted to the 52 which adds a tap to the inlet manifold which is opened when the aircraft is parked to help stop oil pooling in the lower cylinders, but it would still invariably piss oil out of the exhausts when pulling through after any time spent idle. Occasionally it required the lower spark plugs to be pulled out to drain the cylinders if there was enough resistance to pulling through - possible to bend things internally if too much force is applied. There was invariably an oil-slick on the grass when the aircraft was parked outside - there are a few choice spots on the line at Waltham closest to the clubhouse, and I remember a 172 grabbing a spot which the Yak had been parked in, and the pilot then laboriously opening the cowlings and peering into his engine trying to work out where all the oil around his nosewheel had come from.
The 52 has shear-pins on the connection from the engine to the air compressor, and a regular feature of the North Weald formation school were Yaks with no air pressure being wheeled into the maintenance facility to have them replaced, the shear-pins not reacting well (like radials in general) to the throttle being rapidly whanged about, and in the early stages of close-formation training it can tend to be a bit of a throttle whang-fest.
We had another 52 end up in a field due to a broken accessory drive shaft one year - I was part of that formation, took off as a four-ship, split into two pairs, called the other pair later for a rejoin to hear from the one still airborne that the other one had gone down, and they was going to make a low-pass to see if the occupants were OK. All ended well, they arrived back at NW by car a few hours later, clutching a few pieces of broken propeller to put behind the bar. Radials can take a relatively large amount of damage and keep going - YAKH in its time had a cylinder crack open in flight, and on another occasion had the core of a spark plug blow out and wreck some of the HT cabling, but still came home safely (I remember the crash alarm going off at Waltham for both of those) - but the in the case of the NW incident the accessory drive failure killed the mags, and that was that.
Edited by eharding on Monday 6th July 16:03
I guess as with all aircraft there's a preflight procedure - and cranking the motor either by hand or on the starter minus fuel & spark is part of the procedure.
What about big stuff - the R-4360 - I assume this is just cranked on the starter for a couple of turns same as above?
Would hate to foul the plugs - 56 of them.
What about big stuff - the R-4360 - I assume this is just cranked on the starter for a couple of turns same as above?
Would hate to foul the plugs - 56 of them.
lufbramatt said:
was lucky enough to be allowed to have a sit in the "cabin" in that Skyraider, crazy that they are chunky enough to have 2 seats installed in the fuselage! Didn't fancy a ride in there though, not the comfiest of places
Recalling pictures of Skyraiders with long and wide canopies, I wondered if they were used for Carrier Onboard Delivery (COD). It turns out there was, in the form of the AD-5 version, which could seat 4 in the 'greenhouse', plus another 8 to 10 'down the back'. (2 crew + 12 passengers) That's quite a load!Edited by GliderRider on Thursday 9th July 20:23
Relevant video on YouTube:
https://www.youtube.com/watch?v=eyPVVrtLpAo
Made by Mikey McBryan of Buffalo Airways, of the 'Ice Pilots' tv series from a while ago.
The channel is called Plane Savers, great series of videos of restoring an abandoned DC3 as well.
https://www.youtube.com/watch?v=eyPVVrtLpAo
Made by Mikey McBryan of Buffalo Airways, of the 'Ice Pilots' tv series from a while ago.
The channel is called Plane Savers, great series of videos of restoring an abandoned DC3 as well.
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