Safest final approach
 

I'm 10 hrs into PPL(H) in a R44 and have been flying with a couple of instructors - both are excellent but have different advice on the final approach.

On the one hand gently bleed off airspeed with aft cyclic throughout the approach and maintain glideslope with the collective - reach the aiming-spot with no flare.

On the other hand maintain 60 KIAS until 100ft AGL then begin gentle cyclic flare and control height with collective. Level off as airspeed falls to zero.

What does everyone think off the best approach in terms of controlling sink rate, vortex ring state and keeping out of the avoid curve?

A slow, steady approach gets the power and pedal in early (no surprises at the bottom) and gives you ample time to see and miss obstacles.
A fast approach with a flare at the bottom gives you more potential in the event of engine failure or power loss.
If I was approaching to a big flat area that I knew was clear, I'd fly something close to a power-terminated auto profile, so if the donk failed I could just continue doing what I was doing.
However, this is the exception rather than the rule for most pads you go into, so the steady controlled approach is usually the go in my experience.

the trick is to be gentle...
 

Your approach is supposed to keep you out of dead mans curve for obvious reason...

http://www.rnk.co.uk/himan/images/Ex...am_424_566.gif

Give a few more hours and you'll be doing the approach without thinking...

If you set up your decent profile i.e. collective position and 65-70 kts and using just your cyclic you will follow the safe approach path throught the curve. The trick is to be gentle with the cycle and as you begin to near losing transition, gently start to feed in the collective with the appropriate amount of pedal to keep the nose straight, while gently maintaining the attitude with cyclic (actually moving it forward towads the end of the approach) which will ease you back into the hover transiton and into the hover with no big suprizes of loss of translational lift or attitude or direction changes...


Basically.... it's the reverse of what you do for the take off and climb

The H\V diagram applies to the case where full climbing power is applied. The shape of the avoid curve (if there was one) would be completely different for the approach case. If you fly a constant angle approach (about 6-8 degrees) at a constantly reducing airspeed, ie the constant apparent groundspeed technique, you will always be able to make a reasonable EOL from an engine failure anywhere on the approach, PROVIDING THE LEVER IS LOWERED QUICKLY ENOUGH (even in an R22), until you get close to the hover; then hover EOL technique applies.
Unfortunately the above technique puts you in the environmentally unfriendly blade slap condition in most helicopters for a substantial part of the approach. Keeping the speed up a bit then flaring gently obviates this somewhat.
The dangers of a engine failure on the approach (like you have forgotten the carb heat) are that when using either technique, the cues of sudden yaw and lowering RRPM are much less obvious. If the speed is low, RRPM recover very slowly and flaring is not an option since you need to preserve airflow through the disc.

A good set of questions.

The H/V Diagram does not apply for approch and landing, [Ive rephrased this from only applies for take off to make it clearer].

The laws of Physics apply all the time.

We had a test pilot come and talk about how the H/V Curve is constructed at the last Redhill safety evening to try and dispel this myth that you need to stay out of the H/V curve on approach. I am not going to try and quote him here but the fact that the test flights for the curve are carried from level flight at various speeds and altitudes with a delay in the intervention time means that the flight conditions are completely different for those experienced in the descent. He pointed out that most constant angle approaches are in fact made through the curve but under different conditions.

It would be possible to construct a curve for the approach but no manufacturer I know of does it (or publishes the results).

I am with Arm Out The Window, the technique that gets used depends on the area you are approaching.

Rotorfossil gives a good description of how things are in the R22.

Remember your instructors have to hang their hats somewhere and teach you something, personally I hold some speed until later in the approach in an R22 (caveat not current on R22 or R44 but haven't forgotten) , but it can be too much for some students early on to be flaring a bit tighter and feeding in power more quickly at the bottom of an approach.

Assuming you are training on an airfield ask you instructor(s) to demo an engine failure on the approach from a point of your choosing (verbally only) and see where you end up and how you get there. Perhaps get them too talk to one another and set some kind of standard for your training.

Remember the slower you are going the shorter you will fall on the approach (from the same altitude) so losing speed too early in the unlikely event of an engine failure means you might not make the spot.

The link Vital Actions posted has a furher link to some approach photos and for me I cant help wondering why you would teach someone to be where they were taken from over that lake, there is only one place they'd be going IF the engine stopped, so my vote says sight picture good for flat ground beneath, ground track bad for that altitude (with the view seen out of the window).

Don't be too concerned about Vortex Ring, the figures that get taught are quite conservative , don't let the rate of descent develop into something you don't have the performance to arrest, that causes a lot of accidents and the VRS brush comes out to tar them with. The lighter the aircraft is the easier it is to get it into VRS and the easier it is to get it out !

um..... we are talking about a "student pilot" here with 10 hours.... flying at an airport with lots of space, so at this stage I'd think safety, safety, safety.... so stay clear of the curve and in doing so you'll avoid vortex completely. Later on in your training you'll learn about different kinds of approaches into different kinds of LZs. For now stick to the basics and fly safe...

even if the curve was drawn up for take off...

I think the fact that some people think the H/V diagram applies to approaches shouts at the importance of the sort of discussions Veeany seems to be so enthusiastic about. Nobody knows everything, I will be the first to admit to the odd 'light bulb' moment when taking part in or viewing these chats.
Keep asking why. The only stupid question is the one you don't ask!

My tuppence.....the basic difference between the two approaches you describe in your initial post can be described as the US Army method compared to the US FAA method.

The Army taught a constant angle, decreasing speed approach beginning at about 300 feet AGL...and an airspeed of about 60 mph/knots and an approach angle of about 6-9 degrees (as best as I cann remember) for the "normal" approach....and 12-15 degrees for the "steep" approach.

The FAA used the same entry point but maintained airspeed at or above Vtoss until 30-50 feet....then a deceleration to the hover at 3-5 feet AGL. The goal was to carry a bit of airspeed in case of an engine failure or tail rotor failure....one to allow for a bit of Rotor RPM if an engine failure or to provide streamlining should the tail rotor fail. The profile is not aggressive....just holds a bit more airspeed and uses a deceleration at the end of the approach rather than a more gradual constant rate of deceleration all along the approach.

Either method works.

Neither are hard to do or learn.

Neither are unsafe.

If you are flying with two instructors and they are telling you one of the methods is the better and the other is not good....get the two of them together and the three of you settle upon how you should be taught so that you are not fighting opposing viewpoints. Practice both....learn both....use both...but the instructors must agree on what you are being taught.

Better yet....perhaps a CAA check pilot can offer you guidance on how the maneuver should be flown on a license check ride....that is what matters most.....once you get the license...then use whatever method fits the occasion.

Another thought.....High and Slow.....watch out below! Low and Fast....bust yer Ass! Airspeed can be traded for Rotor RPM....height is always traded for rate of descent.....groundspeed at touchdown can trip you up! Look for the happy medium between height and speed and you cannot go too far wrong.

Many thanks for your helpful posts. Obviously there are two schools of thought here - and each has its merits. There is no harm in being proficient at both techniques.

I actually prefer having occasional lessons with another instructor as you get a different perspective on learning how to fly.

I'm with VeeAny and Rotorfossil on this one, re the H-V curve and the rest.
The constant angle approach (tapering airspeed and height together on the approach) has the additional benefit of being the best technique when power is limited: quite often in the case of the R22 when 2-up!
There are other benefits for advanced flying, ie confined areas, night approaches and hilly/mountainous terrain approaches.
And if you have an hydraulics-out approach to contend with, in, say a 206, 120, or 350, it's much better to fly a steady approach than to come whizzing in at 60 KIAS and then try to flare off the IAS, with changing and possibly heavy control forces.

What is "Normal" about that approach?

The question had to do with "Normal" approaches....did it not?

What is Vtoss for the R-22, R-44, B-206 EC-120 and AS-350? 60 Knots??????

You are mixing things up.

Don't know about y'all, but I am liking very much that 'Sea Level @ 1370lbs' sector.

50kts / 200ft looks like a nice place to be ;-)

Following on from the above, I think it's good to develop your skills in managing your available power on the approach.
When approaching to a pad where you'll have significant ground effect (unless you have the room to fly an auto with a big flare and cushion at the bottom), you need to manage the transition between forward flight and the hover carefully so that as you lose translational lift, the 'slack' is picked up by ground effect, leading to your power peaking at the lowest possible amount.

If you go too slow, you need OGE power before you're getting good ground effect; too fast, and you end up flaring into the pad, levelling and causing a large power spike as you pull collective and feed in pedal to stabilise.

After a while you'll get good at working the transition - just keep your apparent closure rate constant and aim to fly your backside down an imaginary set of rails to end up with the mast over the centre of the pad at your normal IGE hover height, and note how much power you use with different closure rates over a few approaches. It's a good challenge, and useful.

Qwikstop
All the best it'll be fine at the end I'm sure, as for a couple of tips.

When we started taking in a large influx of low hour pilots pilots we very quickly found that each school and even different instructors had imparted different techniques in their students.

I.E. a finger print of the instructor which became easily recognisable in many instances. (heh heh, the good and the not so good)

We quickly rationalised that it was not "our" technique that mattered but simply any safe procedure was ok. The main reason for this was that newbies would quickly become a bit unsettled if they were told they were doing it wrong when it fact they were safe, especially if they were a bit uncurrent.

We stipulated a minimum A/S (40 in the '47) for 100 feet and explained and demonstrated why, then those who wavered a bit by forgetting their previous counselling, of not washing A/S off too quickly, soon picked it up. The other bits like circuit height, downwind or base airspeed, doesn't matter a damm.

I suggest you ask and discuss what is the accepted A/S for 100 feet and make sure that bit is common between your tutors.

I also found that the blade slapping profile is pretty much the best, in either the '47 or '22. The sound doesn't go all that far, too bad if it does, learning the best reasons for good technique is far important than worrying about some hairy armpitter that is out to get you for loud noises.

You'll find soon enough that your instructors will teach you different profiles for different tasks, such as confined areas where spending time looking and controlling a slow descent is best. in the mean time just worry about the simple easy circuit.

I found that one of the best check procedures was a persons ability to fly a formal circuit, albeit at any profile - in a safe, precise and consistant manner.

Here is a trade secret, it is what many newbies, and experienced pilots have heard from me;

"any c**ckhead can do a smart ass split ass turn onto the pad, the best can demonstrate precicion.
one's ability to demonstrate precision with a good circuit is a demonstration of one's ability to dedication,
if you are not dedicated, well you can f*** off.

got the message?
good luck
tet

well said tet...

Dont think there is a wrong or right answer here. It depends upon circumstance. The following will make a difference, strength of wind, temp, altitude,restricted site, power available, weight of helicopter. Could go on and on. Personally I teach in a 300 to be have a ground speed of 40 kts with a rod of 500fpm at 500ft.At 200 ft start applying a bit of power this will reduce rod and fwd airspeed. keep that going to you get to the ground. That way there are no nasty surprises at the bottom. Dont forget we are teaching people to ulimately come into a restricted site ( otherwise go fly a plane) who wants to come in at 60 kts ? No time to see the wire line let alone allow the engine to arrest a high airspeed and possible high rod. As for vortex ring what ? Coming into land into wind no way, unless you have, zero wind, about 15 kts airspeed and 800 ft a minplus rod and pull an armful of power at the bottom.

Landings at an airfield and Confined Area Operations are two entirely different evolutions. Techniques learned at the airfield transfer to the Confined Area but are a subset of those used doing Confined Area Operations.

Do you not teach the concept of High and Low Recon (Recce for our UK brethren) and a landing approach that considers the nature of the area you are landing into....some cow pastures can be quite large and some clearings in the forest can be very small and two different approaches would be called for.

I do hope you are teaching "Think" along with the rote memory lessons.

If your question is "what is the safest approach?"
My answer is a perfectly performed auto rotation.:) You can't get any safer than that.

More great advice from chopjock.






Not. :ugh:

SAS:
My point was that the constant angle approach is a 'building block' for other more advanced techniques, and should be taught from the beginning.

Perhaps I should not have muddied the waters with the ref to Hyd-out approaches, but you might be surprised how many there are out there who think that because the RFM says that 'X Kts' is the 'best IAS' hyd-out, they should fly the approach for as long as possible at that IAS: and then they have the difficulty of a large attitude change and rapidly changing control forces to get the aircraft under control for a gentle run on.

In 8 years of instructing modular CPL(H) students (BTW, that's the latest 8 years of being an instructor since 1980, and part of that time in a commercial school of a company in which you and I share previous lives) I can say that the most significant area of preparation that these modular students need for General Handling is in re-teaching constant angle approaches, so that they can cope with limited power and fly the expected techniques on test.