The venerable Bell 47
Avoid imitations
Joined: Nov 2000
Aviation Qualifications: ATPL
Posts: 15,110
Likes: 1,083
From: Wandering the FIR and cyberspace often at highly unsociable times
outofwhack,
Parachutes were worn in the Whirlwind 10 when going to higher altitudes, it was to do with the possibility of an aircraft fire and the low rate of descent in autorotation.
The Flight Reference Cards gave the abandonment drill to be followed (something along the lines of: Open windows, control frictions full on, disconnect mic/tel leads, undo harness, sit on window sill, facing inwards and roll out backwards from aircraft window).
There was a note at the bottom of that page which worried me quite a lot. It said "Warning. Objects jettisoned from the aircraft in autorotation may go through the main rotor disc."
As the pilot, I can't think of another phase of flight when I would want to jump out.....most of us said we would give the cyclic a kick to the left, to try to roll the aircraft way from us.
Being a newbie - dare I ask the question why helicopter pilots dont have parachutes. The old reason of not being high enough to use them does not apply anymore. Base jumpers prove that.
The Flight Reference Cards gave the abandonment drill to be followed (something along the lines of: Open windows, control frictions full on, disconnect mic/tel leads, undo harness, sit on window sill, facing inwards and roll out backwards from aircraft window).
There was a note at the bottom of that page which worried me quite a lot. It said "Warning. Objects jettisoned from the aircraft in autorotation may go through the main rotor disc."
As the pilot, I can't think of another phase of flight when I would want to jump out.....most of us said we would give the cyclic a kick to the left, to try to roll the aircraft way from us.
Joined: Jun 2002
Aviation Qualifications: PPL
Posts: 5,100
Likes: 321
From: east ESSEX
OOW,in answer to your Q about FTH,think of it this way;in an ideal world,ideal engine, on the ground at full power(non turbo/supercharged)( full throttle) you would see a manifold pressure of 29-30"/0 lbs,ie static ambient presure; real life- about 27-28"/-1/2 lbs due to the configuration/losses in the induction system. On top of that, you have a transmission limitation which ,may be 26"/-2lbs,which means you shouldn`t actually use more than that.
Now, as you climb at,say 25", you will need to progressively open the throttle to maintain 25", until at some point the throttle is fully open,or you reach your time limit at max power,and reduce to MCP ,perhaps 23". This may be a transmission limit or engine limit. If you continue to climb,maintaining that limit(23"), you will reach an altitude where the throttle is again fully open, and if you go higher still, the MP will start to decrease. The throttle is fully open ,so there is no restricting of airflow into the carb,which is also doing it`s best to maintain the correct mixture. You can of course still climb,but even with full throttle, MP will be reducing; you may now be only able to maintain airpeed/height at one power setting- more likely you will be anoxic !!
I`m reminded of the Test pilot at Boscombe who was tasked to do a height climb in a Sioux,with oxygen, parachute,etc,who wrote that a stopwatch was irrelevant, a calendar would have been more useful!
2" of MP is approximately 2050 ft in altitude, so you can work the figures for the appropriate aircraft.
If you have turbo/supercharging ,you abide by the same principles,particularly
in helos, since you will have a transmission limit to maintain, but you will still reach an altitude where the throttle will be fully open ,and the boost starts decreasing......don`t forget the calendar, oxygen, blankets etc....Syc
Now, as you climb at,say 25", you will need to progressively open the throttle to maintain 25", until at some point the throttle is fully open,or you reach your time limit at max power,and reduce to MCP ,perhaps 23". This may be a transmission limit or engine limit. If you continue to climb,maintaining that limit(23"), you will reach an altitude where the throttle is again fully open, and if you go higher still, the MP will start to decrease. The throttle is fully open ,so there is no restricting of airflow into the carb,which is also doing it`s best to maintain the correct mixture. You can of course still climb,but even with full throttle, MP will be reducing; you may now be only able to maintain airpeed/height at one power setting- more likely you will be anoxic !!
I`m reminded of the Test pilot at Boscombe who was tasked to do a height climb in a Sioux,with oxygen, parachute,etc,who wrote that a stopwatch was irrelevant, a calendar would have been more useful!
2" of MP is approximately 2050 ft in altitude, so you can work the figures for the appropriate aircraft.
If you have turbo/supercharging ,you abide by the same principles,particularly
in helos, since you will have a transmission limit to maintain, but you will still reach an altitude where the throttle will be fully open ,and the boost starts decreasing......don`t forget the calendar, oxygen, blankets etc....Syc
Joined: Jan 2006
Posts: 79
Likes: 0
From: Canada
don't forget the placard thats in the 47 about manifold pressures for 200 hp at various temps and altitudes...that technically becomes your limiting factor. since your transmission is rated for 200 hp of input hp, if you pull 25" MP at 5000' you'll actually be using more than 200 hp from the engine (you're into the 65 hp of spare power for which the engine was de-rated in the first place). i've never heard of anyone worrying too much about that MP placard, especially since the 200 hp limit is not actually stated as a limitation in any of the FM's that i've read.
Joined: Apr 2004
Posts: 272
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From: ˙ǝqɐq ǝɯ ʇ,uıɐ ʇɐɥʇ 'sɔıʇɐqoɹǝɐ ɹoɟ uʍop ǝpısdn ǝɯɐu ɹıǝɥʇ ʇnd ǝɯos
So do you mean they have physically derated an engine from 265 HP to 200HP with a placard?
I always thought there might be some kind of mechanical stop that does it.
How is an engine physically de-rated?
I always thought there might be some kind of mechanical stop that does it.
How is an engine physically de-rated?
Joined: Jan 2006
Posts: 79
Likes: 0
From: Canada
i don't think i said it was physically de-rated...just rated at less than its full potential so there is some power in the bank for performance loss with altitude. for example, if the engine is putting out 200 hp and working at 75% of its possible output to hit the MP redline, there will be a point at which its working at 100% of capacity to deliver that 200 hp at some altitude/temp. you should never actually be putting 265 hp through the drivetrain unless you're exceeding redlines. its the same idea as the c-20 in a jetranger being 420 hp but only delivering 317 (i think) to the tranny. without that power reserve it would be like...well it would be like a jetbox with a c-18 i guess...(thankfully i never had to experience that)
Joined: May 2000
Posts: 124
Likes: 0
From: Darkest Wiltshire
Bell 47
Hi all,
I've tried Google and not had much luck so I thought I'd delve into the wealth of collective knowledge (no pun intended) on the forum.
Highest hours, and or the oldest operational Bell47. I'm looking for the fleet leader.
Any info?
Thanks
Taff
I've tried Google and not had much luck so I thought I'd delve into the wealth of collective knowledge (no pun intended) on the forum.
Highest hours, and or the oldest operational Bell47. I'm looking for the fleet leader.
Any info?
Thanks
Taff
Joined: Jun 2006
Posts: 100
Likes: 0
From: London
Give Joey Rhodes a try at the Bell 47 Helicopter Association.
www.bell47helicopterassociation.org
LM
www.bell47helicopterassociation.org
LM
Joined: Jun 2006
Posts: 5
Likes: 0
From: USA
The oldest B47?
I have been fortunate to have flown a fully restored B47B model back in the 90's, I believe it was the oldest helicopter still flying at the time. It was owned by the late Doug Daigle President of Tridair Helicopters, John Wayne Airport, California USA. It has now been donated & retired to the air & space museum in Washington DC.
Joined: Sep 2007
Posts: 127
Likes: 2
From: Goathland
Hi, Guy's
There's mine G-BFYI 47G-3B-1 ~5570 hours, made in 1965, mind you, we are just about to get it flyable again after brand new engine, gearbox and tail rotor blades (been a long and expensive year).
Kevin.
There's mine G-BFYI 47G-3B-1 ~5570 hours, made in 1965, mind you, we are just about to get it flyable again after brand new engine, gearbox and tail rotor blades (been a long and expensive year).
Kevin.
Joined: Feb 2005
Posts: 70
Likes: 0
From: Meon Valley
Bell 47 J
Any thoughts ?
Are these to old and rare to be practical in the UK. Are they thirstly and heavy. Does it really make a diffecrence to have the larger engine. Spares ? and are the rotables common with the other 47's
Are these to old and rare to be practical in the UK. Are they thirstly and heavy. Does it really make a diffecrence to have the larger engine. Spares ? and are the rotables common with the other 47's
Joined: Jan 2007
Posts: 46
Likes: 0
From: The Woodlands, Texas
Joined: Apr 2007
Posts: 382
Likes: 15
From: Out there
Bell 47 Tail Rotor Blades
Hey Guys
Looking for a set of tail rotor blades for a Bell 47, anyone got a set to sell. Even a short time pair will do as we're getting very low on ours.
PM me if you can help
Cheers
ET
Looking for a set of tail rotor blades for a Bell 47, anyone got a set to sell. Even a short time pair will do as we're getting very low on ours.
PM me if you can help
Cheers
ET
Joined: Oct 2006
Posts: 268
Likes: 0
From: Florida
Try www.scottshelicopterservice.com. If they can't help, they should
know someone who can.
know someone who can.