Thanks for that 212man, I hadn't come across that as a certification spec - every day is a learning day :-)

Well I would be able to calculate that pretty accurately for the VTOL profile as the test pilots have produced the graphs but I can't compare it to your 'Corner' profile as that would depend on your gut feeling about when to stop your acceleration in order to miss the stadium roof and hence what speed you would reach and therefore what your rate of climb would be.

Cheers
TeeS

Chopjock is a drone operator.
{and has flown as a passenger in an R22 once}.
So be gentle.

Surely you don't think that Vtoss is in any way related to the tail rotor?

Here's an example of a pilot trying to fly your proposed technique:

I was giving a time period in which to answer a question.


That was all too slow, nothing like "my technique". No back up, no firm acceleration and no zoom climb...
I wonder how in that video it would have turned out if that Bell had attempted a Cat A departure profile?

If he had attempted a Cat A departure profile and had insufficient power to fly away, which is exactly what happened, he would have been able to fly safely back down to the departure point.
Maybe the point that Cat A departure profiles are designed for exactly this reason has so far escaped your understanding.

Like this...

You've got it at last Chopjock, that is a perfect demonstration of a class 1 profile (it wasn't called that then). From the hover the pilot flying accelerates the aircraft and the pilot monitoring calls 'groundspeed' when he sees the ground moving past the window and then 'airspeed' when the ASI just begins to fluctuate. At that point, the pilot flying adjusts the attitude and power to climb almost vertically whereupon the pilot monitoring calls '20 feet', '40 feet' and 'rotate' as the radalt shows 50'. At that point, the pilot flying initiates a further acceleration and is committed to fly away - before this point, in the event of an engine failure (or other emergency) the take off is rejected.

This profile allows the S61 to depart from a very short runway providing class 1 performance in the same way that the vertical profile provides. It does not allow a departure with obstructions that would be found in a stadium environment!

Cheers

TeeS

Ok a Class 1 profile takes about 12 to 15 seconds of "exposure" time to Vtoss. A Cat A profile takes about 30 seconds or more. If neither can survive a tail rotor failure during this time, then which is the lesser of the two evils? I would suggest a shorter exposure time...

Laddy....if you think 15 seconds means squat considering the rarity of a Tail Rotor failure.....you ought to stay home in bed all day and pray a Police Helicopter doesn't join you.

Multiply by how often did they do this and was it after 15 seconds when this tail rotor failed?

JimL......There cannot be two such on the Forum.....the odds against that are just too far out there for it to be possible.:ugh:

Again, you're missing the point. The one you linked to showing a S-61 is a "clear area" profile. It needs a specified minimum distance of clear area to operate from. If there is sufficient distance available (such as existed at Penzance before Tescos built a supermarket on it), it would be flown. If not, from a shorter and confined area surrounded by high obstacles (such as Leicester City ground), it can't be flown because the required obstacle clearance or stopping distance can't be guaranteed and a landing following any loss of power would almost certainly end up in the stands.

I understand what you are saying. The linked S61 video shows a large helicopter in a large (ish) space with a clear reject area, so scale it down to a smaller helicopter in a smaller space and a smaller reject area. Risk flaring into the stands in 15 seconds of exposure v spinning out of control at 400 feet with no airspeed and 30 seconds + of exposure?

Care to explain why the size of your chopper is improved by a lack of its length?

On reading the posts on gear retraction and minimum forward airspeed for aerodynamic control why is gear retract based on height should it not be on airspeed i.e. minimum airspeed for control if TR failure then it's down to help cushion the landing.

I believe autorotates are difficult to judge especially at night how about a belly air bag, triggered by under carriage compression rate or a G sensor and why has no one thought of anyway of adding anti torque at low speed if TR failure. Maybe a smallish parachute fired sideways to slow the spin triggered by a yaw rate and time sensor. Just a bit of brain storming.

Chop, more people have crashed doing your corner departure (because it relies on a performance guess rather than tested data) than crashes from TR failures doing Cat A take offs.

Ahh! now it make sense. TC you must be lovin the last bunch of posts. We all on Chopjocks little hook!

CHOPJOCK, I am not going to trash your ideas because sometimes, lack of doctrinal thinking and dogma can be the mother of invention. However, I sorry but in this instance you are "droning" up the wrong tree.

You see the TR is there to stop the torque applied to the rotor head, spinning the fuselage once the undercarriage friction with the ground is not longer present. To make the TR efficient, it is placed a long way down the tailboom to give some leverage. This provides the added advantage of "Keel" surface. That is to say the surface of the fuselage and tailboom combined, when pushed through the air at speed, provides an element of anti-torque reaction all on its own. However, this "Keel" surface is not really effective until the forward airspeed is well above 70-80 KIAS. Now I am not a Test Pilot so my numbers here are just a guess but you can get the idea. The more power you apply to the rotor head, the more "torque" is trying to spin you.
So armed with this new knowledge, you can understand that what you propose, scuttling across the football pitch then zooming over the stand, you will still be below the speed where any benefit from the keel surface is not present. Added to the requirement to apply lots of power, to accelerate quickly, and you can understand that a TR failure anytime during your procedure would leave you, at worse case, moving forward across the ground, spinning like a an angel with a broken wing towards the obstacles in front of you. This set of circumstances is extremely difficult to resolve.

In recognition of the critical role the TR plays, especially in the low speed, low height part of the flight envelope, the certification requirements for the TR system are very comprehensive and the design failure rate much lower than other systems that may for example, be duplicated. This is why this accident is so significant if indeed it proves to be some kind of design fault.

This problem, the heavy reliance on the TR, has plagued designers and performance systems since Sikorsky donned his pork pie hat. It is nothing new.

Many factors come into play when a TR malfunction occurs and the actions of the pilot are just one aspect. Design characteristics, Power Setting, airspeed, height, wind direction etc all have a influence on the outcome.

I understand your concern, hanging around in the low speed envelope increases the exposure to the impact of a TR failure and you are certainly correct in this assumption. However, your proposal does not solve the problem as the exposure remains critical throughout your proposed take-off envelope and marginally improves as speed (>80 KIAS guess) and height is gained.

If you are a Drone Pilot and you do it for a living, big respect. I had a drone for my Daughters Wedding this year and it and the operator were awesome.

I hope this post helps you to understand why so many are perplexed by your proposal.

TC

He is actually a helicopter pilot, having done his PC's for the past 7 years or so ( he is actually a very good handling pilot, including a successful landing with a stuffed tail rotor in an Enstrom and an engine failure in a Hu 369) He is a single engine pilot so is asking why one has to climb quite so high when in a single you wouldn't. I suppose I can understand what he is saying, but he may have a hypothetical point are the manufacturers concentrating too much on engine failures rather than the plethora of other problems.

I think TC knows that - it was a throwaway remark based on some of the ideas Chopjock has come out with.

He could at least have googled Cat A/PC1 profiles to understand them before posting......

If he has survived a TR and an Engine failure he deserves some respect. Certainly experienced more have I have in the last 35 years.

Chopjock,

To reiterate what Double Bogey is saying - you seem to be hung up on the idea that getting VTOSS will somehow protect you from TR failure, and that being under this speed is somehow "exposure".
The reality is you are ALWAYS "exposed" to TR failure - you just may be better positioned if you are say above 1000' AGL with 100 kts airspeed and a clear area in front of you. Anything else, and its not going to be your day.

I was referring to VTOSS simply as a timing reference point for exposure comparison. I am aware if refers to single engine safety speed and will have little "keel" effect, but gaining forward airspeed sooner must be better than backing up with none for longer.

Vtoss is a term that is only used in Category A procedures; it is used establish the Take-Off Distance Required. The definition of TODRH is:

The minimum climb performance required at Vtoss is 100ft/min.

Jim

The AAIB Report tells us when the failure occurred and generally how it happened so we can roughly guess as to the rate and extent of pedal travel and time from liftoff that the Pilot lost control of Yaw.

Perhaps applying that information to Dash and Climb method that is being debated.....to get a good guess at what point the loss of yaw control would occur and thus make an assumption as to what forward speed and height the aircraft would have be at.....would be an interesting comparison to what did happen.

My bet is it would have be at a low height at a fairly low airspeed and probably. not clear of obstacles.....which would be a very bad situation to deal with.

We have to include the take off to a hover, the time required to hover back as far as possible, the time to point the aircraft to the takeoff heading, then accelerate towards the obstacles, hit some speed at or slightly above Translational Lift speed, then rotate the nose upwards, and climb until reaching a safe height above the obstacles.....then lower the nose and accelerate to Vy.....and of course all of the pedal movements that would be required in the process.

What if the yaw control failure happened while in the hover maneuvers prior to start of the take off run?

Anyone care to take a whack at that?

SAS

I think preying to whatever God tickles your fancy is the correct answer for almost ever version being discussed

I would like to have a go at this in a Sim....and see how different scenario's would play out.

Two key issues to me are reaction time and what the initial Pilot action was....and how the aircraft was moving and reacting to the response made.

If the Collective had been put full down almost immediately.....and the nose lowered....would there have been a different outcome (not necessarily a pretty one).

Likewise....had the landing gear been down the whole time....how would that have affected the outcome of any less than controlled impact.

Early on in this thread I asked the question.....do we cause ourselves problems with all the various profiles as compared to the days when we flew the aircraft based upon all engine performance.

That was meant to ask a question similar to what Chopjock is going on about today.

I posed the question by asking if an old fashioned Confined Area Takeoff (Towering Takeoff) would not have been better than the Profile flown by the Pilot in the accident.

I was suggesting the Stadium is just a confined area....and if we did not bind ourselves to the now required profiles....would the outcome have been better in this case.

I reckon the Towering Takeoff method would in some regards not be that much different than the Rearwards Takeoff that was performed except for going vertical and losing visual contact with your Rejected Landing area.

The height required would be less than that reached by the aircraft....but not much.

The basic fact remains....this was a very difficult failure to define quickly (as to cause of the rotation) but the Pilot response would be too reduce Collective and lower the pitch attitude to obtain some forward airspeed.

If the Tail Rotor had a full stroke input....at zero airspeed (or nearly zero), the failure would very difficult to deal with.

One thing for sure is none of us....none.....ever want to be in the situation that this Pilot was that night.

What is important now is to learn as much as possible from this tragedy.

Discussions like this one is part of that process.

We may poke fun at each other on occasions...and even take objection to some things said....but in the end discussion, debate, and even argument can be productive.

SALESS,

"If the Collective had been put full down almost immediately.....and the nose lowered....would there have been a different outcome (not necessarily a pretty one)."

I think - maybe, .....but what you are asking is probably beyond any reasonable expectation of human performance. I tried what I think is the closest approximation available in the 169 simulator, which is the TR driveshaft failure in a similar position. But - knowing exactly what was going to happen and when, in the daytime, over a clear runway, I still was too slow at the first attempt, and crashed. I managed it second attempt. You would have to be superhuman to react quickly enough in the real (unexpected) situation.

REMINDER

Intrim AAIB report 14 Nov
Extract

Failure ?
 

Unless I missed something the AAIB report does not tell that a failure occurred...

Preying on anybody or anything would appear to be a waste of time. How exactly does one prey on God - an imaginary figure? Pray do tell.....

Sarcasm perhaps @pilotmike ?

Yes you missed something....other posters have quoted the AAIB several times.

The AAIB states it is continuing to investigate the apparent loss of tail rotor control.

They do not categorically state there WAS a Tail Rotor Control failure that caused the accident.

Combine the AAIB statement with the Video's that are available and one can easily assume a Tail Rotor malfunction of some sort occurred.

Did the AAIB not state in its Report that the aircraft was responding correctly to Yaw Inputs by the Pilot until the onset of the yawing?

Then add in to your consideration of the AD:s that were issued re the Tail Rotor Control Assembly and ask yourself why that happened very shortly after the accident.

Yes....I would say you have missed something.

...with no advanced warning, he felt the nose of the helicopter drift right. He initially corrected with left pedal; however, the nose continued to drift right.

This is very similar to what AAIB is describing, but with other words taken from one of the many investigation reports addressing unanticipated yaw events. A failure cannot be ruled out but is not mandatory to explain the accident.

Quick question without wishing to draw any conclusion but picking up on what AMDEC has highlighted - without a physical failure/restriction would a LTE event look somewhat different that what is seen in the videos?

You would expect it to recover in the descent rather than keep yawing through several revolutions