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Category A Takeoff: Background

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Category A Takeoff: Background

Old 21st Apr 2019, 14:15
  #121 (permalink)  
 
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Nubian
When you're on about the overcomplexity.... Why did your favourite brand introduce HYD for the R44?? It worked fine with the electrical trim..... (at least when it was working, but why did it need the trim in the first place??) Why did they had that big chunk of tungsten on the cyclic before the HYD was added? Feedback perhaps? On such a light machine?! Should be completely unnecessary!!!
I believe Anfi has said twice he was referring to the tail rotor... And the electric trim was 5hite on the R44.
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Old 21st Apr 2019, 16:41
  #122 (permalink)  
 
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I believe Anfi has said twice he was referring to the tail rotor... And the electric trim was 5hite on the R44
no, he argued that since a 369 main rotor was the same size as a Mi 26 tail rotor and the former didn't need hydraulic assistance, it followed in his logic that the latter, or any other TR for that matter, didn't need hydraulics which is clearly cobblers.
Perhaps he forgets that the 369 had electric trim actuators to reduce the control loads as well - you never know with AnFI, he flip-flops from one part of the argument to another without pausing for breath.

Perhaps he would like to show how a 6 tonne helicopter can have a TR without hydraulic assistance?
I am sure his answer will be that it just isn't designed properly since his ego puts him so far above the legion of designers, engineers and manufacturers who have been making helicopters for many years.

AnFi, have you ever operated a multi-crew helicopter on anything other than a sightseeing jaunt? perhaps you might better understand that having a second pilot is for far more reasons than just giving redundancy for medical emergencies affecting the PF.

Last edited by [email protected]; 21st Apr 2019 at 18:57.
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Old 21st Apr 2019, 19:06
  #123 (permalink)  
 
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A spare engine is only doing BAD STUFF for you, ALL THE TIME, it's introducing extra freewheel, extra explosion risk, extra gear box complication and payload consumed etc etc
It has to make up for it by being useful. The only time it gets to do that is ONCE per million hours. Really obviously not worth it.
A Spare Pilot is useful more than once per 100,000 hours when the other guy has a heart attack.
He is COMPLEMENTARY, that is he actually improves the overall performance of the piloting. This is the highest yeilding safety return.
The spare pilot is useful all the time when used correctly - he is there to monitor the PF when conducting critical manoeuvres, especially IMC - not just to act as the in-flight secretary...

The spare engine is useful ALL of the time since it is not a spare but permits greater capability from the aircraft ( AUM, payload, speed etc) than a single engine helicopter. How many 6 to 8 tonne single engined, helicopters are there btw?
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Old 21st Apr 2019, 20:52
  #124 (permalink)  
 
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crab
The spare engine is useful ALL of the time since it is not a spare but permits greater capability from the aircraft ( AUM, payload, speed etc) than a single engine helicopter.How many 6 to 8 tonne single engined, helicopters are there btw?
I'm not sure you are right there.
Have you considered the Bell 214 v Bell 212 for example?
Or the AS350 v AS 355?

The reason there are not many heavier twin types made is most likely due to the regulations requiring twins...
Ever thought why the K-MAX only has one engine?

Last edited by chopjock; 21st Apr 2019 at 21:18.
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Old 21st Apr 2019, 21:26
  #125 (permalink)  
 
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JimL
The points are serious and answer your questions. Not that complex. (compared to fuel systems of A109, EC135, (S61? 10 fuel tanks?! (how often do you get a fueltank failure? About 10 times as often as if you had 1 I suppose?))) Perhaps you could give a thought to some of my questions there?
and you can see I suffer from being selectively mis-quoted also... (which bit is inaccurate?)

Is it safer for urban overflight in Twins or Singles?
Given the nature of the catastrophic events that occur so often with heavy twins? see post #97

How do you calculate it? OR are you just taking the upside of less engine failure forced landings without the consequential (potentially greater) downsides?
Maybe try answering some of the points, are there answers? Do you have them?
Do you think it takes highly trained / experienced / checked / SoP'd multi crew to stand a chance of seeing the sliveringly thin theoretical upside of engine redundancy? Or can all pilots and operations benefit?
Do you think the 'North Sea model' is really likely to work 'onshore', world wide?
Lots of reasons why it probably won't.
One of which is the disproportionate cost, which prices out most potential helicopter users in order to return an unspecified theoretical gain. Removing the utility of helicopters for a vast number of ordinary people.
Oil / State / EMS are exceptionally highly funded areas, not typical or proportionate to the depth of pockets of the typical civil helicopter user.
What is the COST / BENEFIT ANALYSIS ? Is there one?

Crab, (still v personal my ego has nothing to do with it.)
369 has trim actuators for cyclic loads. Tail rotors don't have a cyclic control, just a 'collective control', called yaw pedals. The 369 does not have trim motors to assist the collective, only the cyclic. It is 'well designed'. The main rotor collective control for a 369 is very light but able to control large thrust. The size of the 369 TR is about the same as the TR of a Mil26, which is a very large helicopter. The pedal forces are a function of the Centre of Pressure being a significant distance from the Pitch Change Axis of the TR blades, this is a function of design and is not necessary, therefore hyd assisted TR pedals are not necessary if the TR were designed to not require such large forces, which is evidently possible. If you can design it without an unecessary system that can kill you then you probably should try and do that. TR loads on HYD assisted AS350 have been known to cause accidents = not better off.

Crab I think you must have mis-read what I say about 2 pilots, you seem to be aggreeing, is that what you intend?:

Crab: "a second pilot is for far more reasons than just giving redundancy for medical emergencies affecting the PF"
Yes that's right, that's what this says:

Me: "A Spare Pilot is useful more than once per 100,000 hours when the other guy has a heart attack.
He is COMPLEMENTARY, that is he actually improves the overall performance of the piloting. This is the highest yeilding safety return.

So to summarise:
a spare engine is only bad until it's useful
and
a spare pilot is only useful until he's bad


(and then the spare pilot concept kicks in)
The Glasgow incident would probably be averted by a spare pilot, but was enhanced by a spare engine."
(and it answers JimL's point, although surprising he didn't know that/had to ask me to explain the difference. If you really wanted safety yield you'd mandate 2 pilots before 2 engines) (Crab: the second engine is a liability (in risk (fire, explosion, freewheel unit failure), weight and complexity, carried for the day it may be necessary/useful, that day has to come often enough to justify the downsides. Does it? (How often must you have an engine failure to negate these downsides?)). The 1950's concept of having 2 engines because one wasn't powerful enough has long gone. The performance/utility of a SE Lynx variant would probably be staggeringly good, weighing 500kg(?) less, doubling(?) it's utility. They still crashed them because of 1 engine failing and there was twice the chance.)

Nubian
Yes you are quite right. I mention that in #97:
"That's not to say 3rd party fatal consequences are impossible from engine failure in urban areas, there's a recent exception in Tampa (and Sao Paulo), very unusual and unlucky, even in a gentle landing like this it can go wrong, hitting wires / poles can do that."

They are extremely rare to end (that) badly, and until those 2 very recent examples, there were almost no cases, but in any case many fewer than caused by 2 engined helicopters in urban areas. Everything is possible and will occur with some frequency, it's really just a case of what that frequency is, how grave are the consequences and whether it's acceptable.
Nobody has defined what is the ACCEPTABLE Level of Safety Performance.


In the UK in the last 10 years the 'scores' for fatalities by engine philosophy are:
TWINS: 49 dead (people on the ground 8)
SINGLES: 13 dead (people on the ground NIL)


The reputational damage to helicopters has largely come from the 2 engine helicopter. (Societal Risk, ask Airbus)
(bigger splash !)

The case is NOT clear.
One hopes that there are serious 'experts' considering these points. (JimL, you? what's the logic?)
Rather than just being blindly wedded to the intuitive 'feeling of comfort' that the 2 engine religion gives.
Given the effectiveness of placebo effect, you can't deny that the 'comfort' plays a part. (especially for SLF)
If it makes you feel better .... you should be free to chose it, but no one should be forced into this dubious religion.


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Old 21st Apr 2019, 21:28
  #126 (permalink)  
 
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In the UK in the last 10 years the 'scores' for fatalities by engine philosophy are:
TWINS: 49 dead (people on the ground 8)
SINGLES: 13 dead (people on the ground NIL)
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Old 21st Apr 2019, 22:44
  #127 (permalink)  
 
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So now you have narrowed your 'excellent' statistical analysis just to UK because worldwide statistics don't suit your argument - that is both barrels in both feet AnFI
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Old 21st Apr 2019, 22:53
  #128 (permalink)  
 
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xxxxxxx
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Old 21st Apr 2019, 23:16
  #129 (permalink)  
 
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Nobody has defined what is the ACCEPTABLE Level of Safety Performance.
You certainly haven't.

They are extremely rare to end (that) badly, and until those 2 very recent examples, there were almost no cases, but in any case many fewer than caused by 2 engined helicopters in urban areas. Everything is possible and will occur with some frequency, it's really just a case of what that frequency is, how grave are the consequences and whether it's acceptable.
Isn't that how statistics work? Sometimes nothing bad happens for ages and then it does? The 2 cases Nubian mentions happened, despite your logic and single engined helicopters with engine problems killed people on the ground - dress it up however you like but a single engine helicopter with an engine failure over a congested area is FAR more likely to have a catastrophic outcome than a twin engine helicopter having a single engine failure........

The pedal forces are a function of the Centre of Pressure being a significant distance from the Pitch Change Axis of the TR blades, this is a function of design and is not necessary, therefore hyd assisted TR pedals are not necessary if the TR were designed to not require such large forces, which is evidently possible.
Do you mean center of pressure or do you mean aerodynamic centre? Do please explain how you will design a tail rotor system where the CP is consistently aligned with the pitch change axis - you understand that the pitching moments change with AoA????

One hopes that there are serious 'experts' considering these points.
a bit like serious politicians considering UKIPs fantasies perhaps
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Old 21st Apr 2019, 23:39
  #130 (permalink)  
 
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Originally Posted by AnFI View Post
In the UK in the last 10 years the 'scores' for fatalities by engine philosophy are:
TWINS: 49 dead (people on the ground 8)
SINGLES: 13 dead (people on the ground NIL)
Go back to school, and learn again the difference between correlation and causation.
AnFI: All Noise, Feckall Insight.

One would have thought that for as long as you've been involved in rotary wing aviation, you'd have run across a clue.
Nope.
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Old 22nd Apr 2019, 00:00
  #131 (permalink)  
 
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Crab ; yes you are right - I have not, (I have suggested some figures) ... but neither have those purporting to:
ref post #118 re ALoSP - why not ??
"Isn't that how statistics work?" yes it is. "dress it up" no need to, that's how stats work, I AGREE

"a single engine helicopter with an engine failure over a congested area is FAR more likely to have a catastrophic outcome than a twin engine helicopter having a single engine failure........" yes true, but that's not the point, that downside has to not be out weighed by the increased fatalities from other consequent fatal accidents, caused by excessively focusing on engine redundancy. (Like those in post #97). It is not clear that happens. It's just a 'nice idea'.

"Do please explain how you will design a tail rotor system where the CP is consistently aligned with the pitch change axis - you understand that the pitching moments change with AoA????"
I do, and I understand when they don't too. You'll have to look that up yourself, it's really obvious, class is closed for today.

Let's get to the bottom of this. I take it you aggree with much of what I say, eg 2 pilots/1950s/some downsides/some upsides
You agree that the upsides should be measured against the downsides and not just upsides in isolation?
It should be measured in terms of ALoSP (agree?), the people considering this issue are not producing this figure.
Why not? because it doesn't work?
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Old 22nd Apr 2019, 00:18
  #132 (permalink)  
 
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Lonewolf 50 "Go back to school, and learn again the difference between correlation and causation." I didn't make any comment regarding cause or correlation, it's just a factoid. What should I be learning about those ideas at school, and why should I learn it again? Always happy to learn, feel free to point out what clues you think I've missed.
"... for as long as you've been involved in rotary wing aviation" - I don't claim any experience, just looking for a logical analysis.

It would be great if JimL could answer some of the substantive points, it would be interesting, he is regarded as an SME. What's the ALoSP?
Should we balance upside against downsides? Is it worth it? How worth it?
What's the CBA? Is there one? Aren't you interested to know? or you already do?
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Old 22nd Apr 2019, 00:57
  #133 (permalink)  
 
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The reputational damage to helicopters has largely come from the 2 engine helicopter. (Societal Risk, ask Airbus)
Here's me thinking that reputation was brought about by the Robbie. You do know the Puma accidents had nothing to with engines, or numbers there of? Perhaps not.
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Old 22nd Apr 2019, 06:57
  #134 (permalink)  
 
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I have to think about this quote
Never wrestle with a pig. You'll both get dirty, and the pig likes it.
Especially comparing a 369 mainrotor with a tailrotor - just from the size ...
Even a smaler BK117 tailrotor takes more horsepower, than a 369 has in total...
But I better stick to the quote ��
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Old 22nd Apr 2019, 08:24
  #135 (permalink)  
 
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ANFI the rules, generally, mandate a “spare” engine to be carried when the helicopter is over terrain or taking off and landing in areas where loss of your engine (failure) would be catastrophic for you or persons and property below you. END OF ARGUMENT.

Loss of the single engine, in a SEH, over or into a congested area, wooded confined area, oil rig, water, scree scattered mountain slope, people, power line etc generally ends very badly. END OF ARGUMENT.

A catastrophic TR or MRGB failure in either a SEH or MEH will end the same way for both machines.

Now I am wrestling with the a pig and more than a little worried that I might be the pig!


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Old 22nd Apr 2019, 08:46
  #136 (permalink)  
 
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I do, and I understand when they don't too. You'll have to look that up yourself, it's really obvious, class is closed for today.
hahaha - that one is just hilarious...........

AnFI, why don't you just admit your agenda is doing battle with the regulators to allow (or not restrict) SEH over congested areas and stop beating around the bush with made-up statistics and circular arguments.

DB has summarised the argument succinctly but you keep banging on about engine redundancy like you have just invented the cure for the common cold.

DB - no, we all know who the pig is but it is fun to prod him now and again
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Old 22nd Apr 2019, 12:02
  #137 (permalink)  
 
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Chopjock
I'm not sure you are right there.
Have you considered the Bell 214 v Bell 212 for example?
look at why the 214 was upgraded to the ST - performance, with safety as an added benefit.


The Bell 214ST was originally developed as a military project from the Bell 214B BigLifter, specifically for production in Iran and the development by Bell was funded by the Iranian government.[2] The fundamental difference was the replacement of the Model 214's single Lycoming LTC-4 turboshaft engine with two 1,625 shp (1,212 kW) General Electric T700 engines, to improve the helicopter's hot and high performance and improve safety.
As for the Kmax - it has a single purpose which doesn't include CAT.
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Old 22nd Apr 2019, 14:18
  #138 (permalink)  
 
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Funny story:
Years ago the Pope came to visit Canada.
The Vatican "Aviation Expert" wanted to have the Pope transported in a CH-47 or similar because it had two xmsn gearboxes and that "in the event that one failed they could continue on one to a safe landing on the other".
There was total silence in the room! (Well there may have been some muffled laughter).
We ended up flying the Pope in a 205A-1 with blue bed sheets roughly stitched over the bush seats. LOL
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Old 22nd Apr 2019, 14:18
  #139 (permalink)  
 
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Originally Posted by chopjock View Post
Nubian


I believe Anfi has said twice he was referring to the tail rotor... And the electric trim was 5hite on the R44.
Hehe, Chop Chop!

I know very ''well'' how the trim worked, thanks...

Now, I wonder if you 2 geniuses can't just contact MIL and ask them why they don't develop a single engine MI26?? You guys are brilliant! For sure, it would be saving the weight of the ''other'' extra deadweight, combining gearbox, and all those extra bullshit systems not needed. Leave out the HYD systems, as that just complicate stuff...and a real Chop/AnFI designed machine would need only 1 pilot (with fairly strong arms) to fly it. When you're at it, maybe you should ask Sikorsky as well, why the hell they have been making the S64/CH54 all these years with 2 engines...Completely waste of time and efforts! Those were sure as hell not made with regards to overfly congested areas and CAT operations according to EASA regs.

Yeah, the Kamax is a real great example no?! What a success story....

As for the 214's, originally planned exclusively for Iran and military use. Khomeini changed that plan...
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Old 22nd Apr 2019, 14:55
  #140 (permalink)  
 
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Originally Posted by AnFI View Post
In the UK in the last 10 years the 'scores' for fatalities by engine philosophy are:
TWINS: 49 dead (people on the ground 8)
SINGLES: 13 dead (people on the ground NIL)
AnFI,

Without more info on the numbers, you don't have a case.
Can you from your numbers above, perhaps tell us the number of flight hours generated for twins and for singles, so we can divide the dead per hour? You can keep it for the UK for now, and we get the numbers world wide later.

Maybe you can give us a list of controlled in flight engine shut-downs (twin), due to some sort of problems, where the result was return to base, land and do some extra paperwork vs. Single engine failure, forced landing/crash and even more paperwork done by someone else?! Also per flight hours? The UK would do for now.
Preferably, split into private/corporate non AOC work vs. commercial operation.
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