Pinnacle Approaches/Limited power approaches

[highfinal]

Morning all,

I had a quick question regarding operations outside the confines of the training environment with regard to the two approach types mentioned in the title.

With regards to pinnacle ops, whether they be to man made or natural spots, it seems to me that most of what i see is shallow approaches, although the training I am supposed to provide is all about the steep approach, for some valid reasons, and some questionable in my mind. I know there was a thread on this a while back but couldn't find it.

The other thing is limited power. JAA vs FAA says Steep vs Shallow respectively, both with a valid argument about the keeping yourself out of trouble with respect to the power curve and altitude.

Can some operators who regularly use their machines in these environments outside the artificial training environs give their thoughts? Be very interested to hear them as the pucker factor teaching students can get pretty high sometimes!

Thanks

[NickLappos]

IMHO, steep approaches require more power at the bottom, and are not recommended when short of power margin. A shallow approach allows you to decelerate more slowly, and track the power rise as you slow down along the power required curve. It allows you to more easily execute a fly away if the power proves too little, because you can simply accelerate away and not have to overcome the higher rate of descent inherent in a steep approach.

How to make a controlled power approach:
1) Above the landing place, briefly increase collective to see how much power you have, pull max power and note the torque or MP. Remember this number, it is your life's blood at the bottom of the approach.
2) Choose a shallow or flat approach, begin a slow deceleration along the approach, carefully noting the power rise concurrent with the speed decrease.
3) as you get slow, look for the power to rise within 10% of the maximum power, and note how much speed is left to lose. If you have only 10% power margin left and you are above 30 knots, wave off. (To wave off, just lower the nose a bit, and increase collective to just below max power. Virtually no descent below the wave off decision point should occur.)
4) As you decelerate further below any indicated airspeed, keep one eye on that power, if you get within 5% of max, and you cannot just terminate at a hover at you landing point, wave off. Practice waving off at this point by just lowering the nose to accelerate a bit. Even a few knots of accel should convert the shallow descent into a slight climb.
4) As you terminate the approach near the landing point, note the power at its peak, usually just as you settle into the IGE hover. You should see that it has no greater than that needed to hover at 2 feet wheel/skid height. Even a momentary increase above this min hover power indicates that you decelerated a bit too aggressively near the hover.

[thecontroller]

the JAA say do a steep approach if power is limited? eh? thats not what i was taught on my PPL. i was taught a shallow app. steep seems like a daft idea

[SirVivr]

highfinal
Try the following threads:
http://www.pprune.org/forums/newreply.php?do=newreply&noquote=1&p=2785881
This is a long one, but many pearls of wisdom:
http://www.pprune.org/forums/showthread.php?t=157357&highlight=elevated+decks&page=6
Good reading,
Chas a

[SirVivr]

highfinal

Another thread.

http://www.pprune.org/forums/showthread.php?t=210633

Chas A

[highfinal]

Exactly what i was looking for - thank you Charles and Nick. Your kind of posts are the reason I keep reading pprune. Keep up the good work guys :ok:

[gulliBell]

Yep, I agree, Nick is a gem of knowledge in this forum.

I would add that if you were teaching your students steep approaches to pinnacles, I just hope they don't end up in PNG or they will very quickly wind up bent up, and no-one likes a wound-up bent-up helicopter pilot :*

[Rich Lee]

Nick Lappos wrote:
Above the landing place, briefly increase collective to see how much power you have, pull max power and note the torque or MP. Remember this number, it is your life's blood at the bottom of the approach.

There are so many acceptable but different techniques for helicopter pinnacle landings that I rarely take issue with one or another however, the comment quoted above concerns me if it is intended to advocate coming to a hover above a landing area to check power. An OGE power check above a pinnacle can lead to a valid assumption based on false premise because without sophisticated instrumentation you cannot be sure you are in a stationary hover and you cannot accurately calculate the winds; both of which can cause wide variations in the power required to hover.

The more valid method is to calculate actual gross weight, record pressure altitude, record outside air temperature and use the helicopter performance charts to calculate HIGE and HOGE power.

A power check should have been performed at the beginning of the flight to ascertain any performance losses. If less than specification power was available then more than calculated HIGE or HOGE power will be required. Turn off bleed air (e.g. cabin heat or scavage air) or any other device that takes power from the engine if the engine power reserve is limited. The surface and shape (to include obstacles) of the landing area determine which landing, HIGE or HOGE, is required and the angle of the approach. Wind direction and speed is also very important with the primary consideration being to avoid downwind approaches where possible. When a steep approach is used care should be taken to avoid descent rates and air speeds conducive to vortex ring state.

[Giovanni Cento Nove]

Along the lines of what Rich Lee quotes......
There is an endorsement required to operate in the mountains (i.e.) landings above 1000 odd metres from memory) and the methodology is that you use the Performance section of the flight manual and extrapolate from available Met data the OGE and IGE capability.
Whether it is an actual requirement, I can't remember, but you shall not land there for the first time on any mission unless you have OGE performance. Subsequent landings can be at IGE performance.
Seems to work!
And also not mentioned is the approach from below. As your speed decreases and more power is required you can monitor both and make a determination as to how things are progressing. If you reach maximum it is easy to let the aircraft turn around (i.e. gentle torque turn) and return to where you came from. This is the preferred method where you may have no option but to make an approach with a tailwind. Everybody mentions the pinnacle and ridgeline approach but not the one that is halfway up the mountain with one way in and out! Try a steep or shallow approach with a tailwind in the mountains and it is the perfect setup for vortex ring state!
Remember, you can meet all the requirements and methods mentioned here and it can still beat you.
(Exact details ommitted to protect the innocent - go get someone to show you!)

[[email protected]]

The power check Nick suggests is just to make sure you know what the engine is producing at the altitude you are intending to land/hover at - it is not a hover power check (hopefully you have done the pre flight planning from the performance graphs). The problem is that the manuals assume a certain level of efficiency from your engine that might not be available due to damage/wear or even different environmental conditions at the landing area from those you were expecting and had planned on. So to make sure the pre flight planning is valid, you pull to full power to ensure it is available without Nr decay or exceeding other limitations. We advocate doing it within 500' and 5 miles of the LS.

As to the technique for pinnacles, there are many ways to skin a cat and mountain flying isn't a 'one size fits all' discipline where you can use just one style of approach for every situation. At night when visual references are limited we try to follow ridge lines into pinnacles or approach up the mountain - in both cases trying to get rate of closure information early in the approach but this is not something you would do if you were power limited, we operate with a minimum of a 5% thrust margin above OGE.

Using the wind to your advantage and staying on the updraughting side of the feature (even if this means coming in sideways) is healthy, especially if it is very windy and as a general rule avoid losing translational lift until you are sure of making the landing point.

I think the steep approach to a pinnacle is often advocated in the situation where you have insufficient power to hover OGE and the aim is to fly straight to the IGE hover or to the landing without losing translational lift until you are over the LS.