What's a "maximum performance takeoff abort - backwards." ?
 

Is this something you do with float helicopters (Mariners) ?


NTSB Identification: SEA04CA122.

14 CFR Part 91: General Aviation
Accident occurred Monday, July 05, 2004 in Hillsboro, OR
Probable Cause Approval Date: 9/29/2004
Aircraft: Robinson R22 Mariner, registration: N856HA
Injuries: 1 Minor, 1 Uninjured.

The flight instructor reported that they were in the process of practicing

"maximum performance takeoff abort - backwards."

The student was on the controls during the maximum performance takeoff phase to an altitude of about 150 feet above ground level, and the instructor took over the controls to demonstrate the abort procedures. The instructor took the controls just prior to call for the abort. When the abort phase began, the instructor applied aft cyclic and slightly lowered the collective. The helicopter had been in a tail low attitude and started to descend into "settling with power." The instructor applied forward cyclic and lowered the collective, however the helicopter did not have sufficient altitude to level out or gain airspeed to recover before impacting the ground on the right side skid. The helicopter pivoted around about 180 degrees then rolled over onto its left side.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's failure to maintain aircraft control resulting in an uncontrolled descent and subsequent roll over. Low altitude flight and the pilot's encounter with settling with power were contributing factors.

I haven'theard it called that, but it sounds like trying an abort from a CAT A / CAT 1 take off. This can be where you depart up and back,so if you abort prior pre determined decision height, you have the deck in front of you. This profile is as far as I know for twins only, and supposedly ensures landing spot until at a height to clear the rig and enter auto if needed. I really don't know all the details, so maybe someone with lots of rig experience can fill in a bit more.

My reading of the same report gives me a different interpetation of what happened....

"When the abort phase began, the instructor applied aft cyclic and slightly lowered the collective. The helicopter had been in a tail low attitude and started to descend into "settling with power."

It sounds to me like the aircraft was moving up and maybe forwards and as in an attempted takeoff at marginal power does not work....he was trying to land back at the takeoff point. If they were facing into wind...he could therefore have backed into his own downwash and the rest as they say is history.

I did not take it to be a rearwards takeoff but rather a rearwards reject. All the more reason to utilize the non-American method of rising vertically until clear of the barriers by a safe margin then starting your transistion into forward flight. The American method that evolves from the US Army method as adopted by the FAA uses a forward movement all through the takeoff to clear the barriers by a safe margin....which means one gives away clear way prior to clearing the barriers.

Long ago I adopted the Non-American method....in that I take the best from the many different ways to answer the same question.

SASless,
"non american method".... That's interesting, never heard of that.
Is there a non american method for landing in a confined area as well?

I am currently clearing land in my back yard for an approach, so this is of interest to me.
Thanks,
slowrotor

Once again, words get in the way of good communication.
What exactly is a 'maximum performance takeoff'? I've never seen it defined any place, so if any ppruners can show me an official definition I'c be grateful.
Does it mean 'using maximum power available', or does it mean 'simulating no more power is avalable and this is all the performance I'm going to get'.
Does it relate to a vertical takeoff? or having to do a level acceleration from a minimum skid height? Or what does it really relate to?
(I'm thinking that there will be at least three official definitions....)

Shawn,

My take on this is much as I said earlier. My training was in the US Army, and much of what I see in the FAA handbooks is exactly the same as I recall the Army techniques to be.

We had normal takeoffs, max-performance takeoffs, and confined area takeoffs. Our British friends have normal takeoffs, towering takeoffs, and confined area takeoffs. Similar concepts....different names and except for the confined area takeoff...pretty much the same techniques.

I remember max-performance takeoffs as being vertical ascents to 100 feet agl then a transition into forward flight. Towering takeoffs at Redhill were the same maneuver.

It would be an interesting exercise to compare the CAA/FAA/MOT handbooks for helicopter flying....to see how the various topics compare.

My understanding of it is/was that you climb from 'skids light' on the ground and pull the maximum manifold pressure available (based on OAT and field elevation), then when you reach the require height to clear the obstacle your transitioned into normal forward flight attitude.

PW

Pilotwolf -I recommend using maximum power required rather than maximum power available.

Not a CFI but believe to demonstrate and teach the procedure a maximum mp is agreed rather than use all the power available. I know a CFI who will put his hand on the collective to stop it going any higher to demonstrate what happens when you try to pull power you do't have.

PW

This may help in the description and problems associated with a max performance takeoff.




http://www.copters.com/pilot/max_takeoff.html

I confess that just from reading the accident report, I have no idea whatsoever what the instructor was doing or why. He says the aircraft was in a tail-low attitude when he initiated the abort, which may indicate that the takeoff was being done to the rear, but I can't tell from the narrative if this was the case.

Perhaps another case of a low-time instructor teaching something he didn't really understand. Can't tell that either, though, without more information.

Thigs that make you go hmmm..

I kinda have an idea of what he was trying to do. One thing I see alot of guys do is on there Max Per T/O is pull in all the power rise stright up or real fast on the departure path to clear all the obstacle's. In the real world flying light singles in feild this doesnt always work and has a few disadvantges:
Remember most fo the time you are at MGW limits:) big drillers, juggies, fire guys etc and are heavy on fuel.

I look for the least steep approach out of there (not always directly into wind).

Pull in max required power and very SLOWLY depart on my departure path (usually moving forward slightly if possible). The reason I go real slow and controlled and try and keep that constant angle is if I am not going to be able to make it I can back down to the the same path to my spot. Lot of thing can happen, I could be too heavy for conditons, the wind could be 100% different at the tree line, I may get a light that requires me to land asap.

Well I dnt know a whole lot bu thats what i do , and I can see what the instructor may have been tryingto do.... Just wait unitl he sees how confined these confined areas can relly be!

RB

What is a "Maximum Performance Takeoff"?

Boiled down, you have a set of priorities:
1) Don't get anybody killed
2) Don't crash
3) Don't damage the aircraft
4) Don't violate any rules/FARs
5) Get out of the area as planned

"Maximum performance" has two facets:
First, it means extracting maximum required performance from the powerplant and rotor system, in order to minimize the time spent in an unfavorable portion of the H/V curve, and to ensure that you are clearing hazardous terrain ASAP. Some will say to always keep a little power in reserve "just in case", but if you end up needing to tap that reserve, it would have been better if you had been using it all along, as you would have been that much higher. If required, use all the power you have until you don't need it anymore. (I restate the obvious when I say that optimum RRPM is part of maximum airframe performance)

Second, it means utilizing the flight path that will ensure the maximum aerodynamic performance. For example, if you have the room to get to ETL while still having an abort option, take advantage. If you know that the wind will be stronger once you get above the treetops, you might choose to ascend vertically until you get the added wind, then move forward, ect.

Again, there are too many variables to lay out THE WAY of doing a "max performance" takeoff, but there are a few guidelines:

-unless you are getting shot at, you must ensure that you can safely abort the takeoff up until you know that you will definitely make it out of the area. If you almost get out, you want to be able to return safely to the ground.

-in the balance between possible hazard from engine failure vs tangible hazard from challenging the obsticle, choose the best odds, but minimize the time spent hanging off of the engine. I'd rather spend 15 seconds hovering at 100' than five seconds watching trees looming ever larger while wondering if we're going to make it.

-your goal is to minimize the time spent with poor options, and to balance those options in favor of survival if the worst happens, keeping the original priority list in mind.

You want to get the aircraft out of the area with the maximum level of safety possible. You are always balancing the small (but omnipresent) chance of an engine failure against the larger chance that pilot error - miscalculating performance, misjudging wind and distance - will force an aborted takeoff, or possibly lead to settling if you are "hovering back down" after almost getting over those 150-foot trees. You are better off to trust the engine rather than your ability to infallibly judge how the aircraft will perform.

Hope this helps

I'm surprised all you experienced guys haven't really heard of this. . .

Max Performance take off is distinguished from a Towering take off by the fact you need a few feet between you and the obstruction.

As you lift you inch it forward immediately in the hope you will gain ELT (12kts - ish) and pull in more lever as soon as the power is available.

Never heard of an abort procedure for this but I assume the chap above (as previously stated) was trying to get back to where he started from. . Not good.

If you don't have the room or the power a vertical take off spinning to the right (non-French) will save you valuable power. . . Don't know what this is called but . . it really works.



:ok:

Mr Selfish
 

You serious? ELT on main rotor.

Don't know - I asked my instructor the same thing after the demonstration, I guess thats where pure skill comes in. . ?

In this case, I don't think I would have lowered the lever. I think it might be better to keep the ROD below 200fpm If not possible try for fwd speed in another direction . . and perhaps spiral back down?

But hey, what do I know. . :hmm:

!!!!!, I meant ETL - Effective Translational Lift (just got back from France, sorry)

For a definition of maximum-performance take-off, see the Rotorcraft Flying Handbook, the official FAA text on helicopter (and gyroplane) flight training. The maneuver is as Sasless describes it, and does include forward movement as soon as the climb is started. This is what examiners are supposed to look for, and what CFIs are supposed to teach.

The question of what to do if you can't make it out is never considered, apparently. A vertical climb, allowing a vertical descent, or even fall (in case of engine failure) to a spot you know you can land on (you just did) is a far superior move IMHO.

I have been teaching both JAA & FAA sylabus recently, and for what its worth this is the short hand of what I taught at the school I worked at.

FAA. maxP take off:

From low hover OR surface to lift off and maintain attitude for either VX or VY depending on what you need, but usually VY. Power (TQ /MAP) often being limited to simulate higher DA. Once clear, accelerate to normal climbout. Height over speed, then speed over height to increase safety margin if it all gtes quiet.

JAA:

First option is to try the VERTICAL take off, with a controlled steady climb (no stick stiring either). If unsuccessful, note max power available AND make judgement of obstacle clearance shortfall and available distance.

Descend in controlled maner, using the front and side transits to keep your landing spot below you. The towering take off is then used (if you judge it will work) and using the same vertical transits, break hover verticaly and at a higher rate of climb, before loosing ascent rate, transition very carefully into forward flight.

So basically the towering is the same as an FAA maxP, but it starts forward transition at almost obstacle height .

Brian:
What is VX in any particular helicopter? The number is never published, and not required to be in any flight manual I've ever seen.
If you have enough power to climb vertically from OGE, then VX is going to be zero. If you don't, VX is probably somewhere below where the pitot system works sensibly.
VX is not a term that I've ever seen in a helicopter flight manual.

Terminology again! Love it.

In Oz we would call this manoeuvre a limited power take off. When I went to the states on UH60L and was asked by my instructor to demonstrate a "max performance take off" there was just the two of us on board, and half fuel. I promptly asked "are you sure you want to do this?" not for a minute realising that what he wanted to see was a limted power take off. When he replied "yep, sure do son" I got clearance for take off at the sattlelite airfield we shared with 9 other Black Hawks, lowered the nose sharply and pulled to 100% matched TQ and jeepers, didn't we take off? Instructor goes white going through 60 kias at over 4000fpm up and the guy in the tower yells "yeehar Aussie go get em"!! We decided to check terminology after that!

The accident report is, I hope, not the full report. I make the following off the hip observations about the report, but accept that I wasn't there and therefore do not really know the story:

Firstly, the report predictably blames settling with power. As do 95% of US accident reports where they really are not sure what happened. As most of you will be aware, we have had a concerted campaign on other threads to rid the world of this misleading terminology, and replace it with Vortex Ring State (VRS), because that is what it is. This will avoid confusion with the term "power settling" which is also problematic and better called "insufficient power".

Secondly, there is no way that this accident was VRS. Do a search on this topic in pprune and read the posts by Nick Lappos (lets not get into that arguement again here).

Thirdly, from the report it appears that the instructor was teaching aborts, but for some reason took over when the tail was already low, and then allowed the aircraft to go backwards whilst lowering the lever. My first observation about this is that it seems strange that an instructor would break an instructional sequence down like this as it easily leads to confusion. Why wouldnt the intsructor demonstrate the whole sequence first, then get the student to fly the whole sequence so as to avoid these kinds of confusion creating situations?

Fourthly, Once he had placed the aircraft into a backward, tail low low power and OGE situation, it will require alot of power to recover. This suggests that the mistake became an accident due to lack of available power to recover from the situation he placed the aircraft in, particularly given that he would have to pass through some turbulant air from his downwash in the recovery. As he passed through some turbulance, and applied max power but was still descending, it is tempting to assume you are in VRS, but almost impossible. This is simply an "insufficient power" situation where there was insufficient power to arrest the rate of descent set up.

I must add that VRS is a very understandable assumption, and I would question whether or not I would have picked up the differences in time to avoid the accident, but I doubt it.

What we can learn from this one is ensuring that when teaching limited power operations you ALWAYS have an out. There is no point practicing bleeding. Use an obstacle like a single tree in a field and get as close to it (or as far away) as you like to set take off area distance, and aim to attempt to fly over it pretending that it represents a solid wall in front of you. Use an artificial power limit BELOW the power available so you DO have a power margin for recovery. If it all turns to worms, you simply head either side of the tree into the clear field and use your extra power available to recover.

But all this is in hindsight. And hindisght is the view of an ar5ehole.
:ok:

Shawn,

I tend to agree with you that Vx is a less than useful concept in helicopters due to the ability to climb at zero speed; it is also correct that due to the inability of the ASI to operate at low speeds it is difficult to set or note the passing of other esoteric points such as Vstay-up on a twin (we might wish to use this for analysis of low speed operating regimes on systems such as HOMP (flight data monitoring)). (The UK CAA is at present seeking to establish an accurate method for low airspeed measurement (to be used only for post-flight analysis).)

However, with respect to the subject in hand, Prouty does give some guidance on the techniques for limited power take-off and also describes a method to establish the best angle of climb - at the end of his paper on Critical Take-off.

http://safecopter.arc.nasa.gov/Pages...L_TAKEOFFS.pdf