Safest final approach

[Qwikstop]

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?

[Arm out the window]

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.

[Flyting]

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

http://www.rnk.co.uk/himan/images/Ex10/HVDiagram_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

[rotorfossil]

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.

[VeeAny]

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 !

[Flyting]

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...

[Flying Pencil]

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!

[SASless]

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.

[Qwikstop]

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.

[idle stop]

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.

[SASless]

if you have an hydraulics-out approach to contend with,

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.

[SilsoeSid]

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 ;-)

[Arm out the window]

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.

[topendtorque]

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

[Flyting]

"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.


well said tet...

[Hughes500]

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.

[SASless]

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.

[chopjock]

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.

[Bravo73]

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:

[idle stop]

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.

[SASless]

I can agree with all of that....especially the part where rigid adherence to procedures without full understanding of what they do not tell you, being the key to long life and a rugby football looking Liver.

The most enjoyable teaching I did was in Simulators.....usually the most effective way of doing so was by having a cuppa tea while those being trained watched the in-flight video of their flight which had just ended in tears. Upon their completion of the entertainment one could then begin anew without the obstacle to learning they had arrived with....that being we are the "Bee's Knees" because of who we work for and how perfect we are in every way.

I watched one very good exercise when a fellow instructor had pointed out a small minor flaw in a Bell 212 Emergency Procedure our company in common held to be much better than which was being taught. I had recused myself due to one of the two being trained....as he and I did not swap Christmas Cards after sharing a house in Warri for two years.

The question centered around what to do if one had a Runaway Up on one engine while at a hover.....we suggested the Company Procedure if followed would result in a massive overspeed and subsequent major expenditure for new bits. The procedure said to land immediately and sort out the problem.

The thought there were more than one way that Runaway Up could occur had not been considered. One cause does not respond to throttle reduction....which means the Main Rotor can reach a surprisingly high number if the aircraft is sat on the ground at minimum pitch.

Immediately upon telling my instructor buddy....."We know bloody well what we are doing....your job is to run the Simulator...not criticize our procedures!"

You know what happened next.....Peter B and the two of us in the rear, got a huge laugh out of the results, and someone else got really red ears!

Teach'em to think....and accept one can and should learn from everyone he shares a cockpit with....that is the secret to long life in our profession.

[jetA1pilot]

QS - Kudo's 2 u for posting and taking on conflicting instructors/techniques. There's been some good gen here that hopefully you can put to good use.

One useful rule of thumb, from an ex-airforce instructor, given to me early in my training was simply this - 40 kts till 10 feet will keep you on the right side of the curve on most days. That one rule has stood me in good stead from R22s thru to 412s.

It's a good ROT which works well for 'normal' approaches in most situations. Try it out sometime, starting the appr from a normal stabilised gate (e.g. 60kts @ 500'). Since it's quite a 'broad' ROT it allows the student to relax a little and get his head up, eyes outside and not fixate on the ASI/ALT combos.

One of the most common mistakes we find with newbies is they often end up in a high hover (OGE) 30-40 feet short of the landing spot, which is a bad place for them to be.

This rule of thumb can sometimes help by simplifying the approach process. Sometimes it helps to uncomplicate things!

Good luck!

[GeorgeMandes]

As I mostly land off airport, 40 knots at 10 feet would not meet the criteria of a stabilized approach in the mountain environment, and seem to be oriented more towards an emergency procedure than a normal landing.

How about have the disk loaded early on the approach, and before decelerating thru translational verify sufficient power reserve to be able to continue the approach to your landing spot or abort and go somewhere else. This also minimizes yaw at the bottom due to changes in power, allows you to better feel the wind and changes in direction and velocity by observing crab and closure rate, and takes away any surprise as to what power you will have available at the bottom.

[Flyting]

People..... we're talking about a 10 hour student, who is learning the basics of a standard approach in a standard circuit at an airfield.... Not a 100 hour plus student learning tight confined area landings and mountain approaches. Hell, anybody got any advice on a rig approach for the poor chap.... no wait.... here it is... http://www.pprune.org/rotorheads/366564-night-offshore-landings-new-approach.html this might help...

Even though there is a lot of useful information that has been given - for training further down the line.... it's a 10 hour student...
:ugh::ugh::ugh:
lets not confuse him...!

[kevin_mayes]

Sorry but I still crap myself everytime I land..... What with the vortex ring and dead mans curve...
Gosh. gosh gosh....
Kev

[Hughes500]

Kevin

Forget about vortex ring, you will not get into it when making even a crap approach into wind. The dead mans curve again dont worry about it, the chances of the engine failing while in it are so remote you are more likely to be run over by the no87 bus going down Oxford street

[Bravo73]

Hughes500,

I think that Kev probably had his tongue firmly in his cheek when he said that... ;)

[herman the crab]

Have you seen how they drive those buses Hughes500? :)

HTC

[Hughes500]

HTC

Been 25 years since I lived in the capital !!!!!

[John R81]

But the 87 is still running, so "run over by one" still possible:=

[Lightning_Boy]

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

Flyting :ugh::ugh::ugh:


Are you stark raving mad!!! Don't be teaching the guy this.


The H/V curve is for take off and NOT landing.

[chopjock]

The H/V curve is for take off and NOT landing. I'm sure someone will correct me if I'm wrong, But I do not believe the H/V curve only applies at take off.:)
It would also apply for example, when ever the aircraft is within the shaded areas, right? which can include low flying (for example hovering at 150 feet). You would not, for example approach vertically from 500 feet with zero airspeed, because if you did, you would be within the shaded areas. Therefore the shaded areas of the H/V curve are to be avoided, including whilst landing.:)

[[email protected]]

Back to the original post - neither technique is wrong or unsafe just subtly different.

The best argument for a constant angle approach is that it requires the student to demonstrate the ability to fly glideslope with lever ie keep the landing point in the same position in the windscreen - this has huge benefits when coming to night/mountain/confined area techniques. He then just controls rate of closure with cyclic.

The other approach manintaining speed is more flexible and probably used more in the real world for an approach to most HLS when power isn't a problem.

I would make sure a student can fly a constant angle approach properly first and then introduce the gate approach/quickstop technique or whatever else you want to call it.

If you approach into wind you have to grossly mishandle an aircraft to get into even incipient VRS so there is no need to be paranoid about it.

[parabellum]

We were taught to pick the furthest of four white circular markers on the airfield and keep it in the same position, relative to the widscreen, through out the approach. Confined area and minimum power approaches came later in the course.

[Scissorlink]

what the last two said

[fluffy5]

The both techniques for ploughing in a robbie have their good points and not so great ones.
The 60kts at 100ft and then flare to come to the hover is an old technique, that I know of used in the Uk for a while, Keeps you out of the avoid curve, but when training the students and the subsequent solo's, it was found alot more incidents with stinger strikes, very close calls and instructor heart failure.
The now maintaining a constant rate of closure, constant angle of approach.
Allowing the speed to slowly wash off when starting an approach, the student has an improved judgement to not to stack it when coming through 100ft, yet you do get some interesting students that will not understand the concepts and allow the speed to decrease to a certain point on the approach to an unsafe level.
None is right, none is wrong. Its your judgement of the students ability for him to judge closure rate and then make a decision.
fluffy

[[email protected]]

Fluffy - what you describe is exactly the result of a student not controlling glidepath with collective - they end up getting steep and washing off the speed to try and keep visual with the landing point - then with no more speed to wash off they resort to dumping the lever to recover the required sight picture.

BTW there is no unsafe low speed on approach as long as you have the power to hover OGE - you can make a vertical descent if you want to. As someone posted earlier - a good marker of student ability is that they can make a safe, steep approach into an LS.

[oldbeefer]

Crab - interesting that CFS have moved to a constant speed approach for ccts on their course, but the DHFS continue with the speed reducing version that we have always used for basic transitions.

[jetA1pilot]

QS, Just a comment on the H/V diagram (avoid curve);

It's a bit worrying that some on this thread have said that the H/V diagram applies to the take off phase only. Hmmmm.....:ouch:

To quote from Bell training: "The height-velocity diagram defines the conditions from which a safe landing can be made on a smooth, level, firm surface following an engine failure"

The avoid curve deals with energy - kinetic (speed) & potential (height), required to regain rrpm following it's enevitable decay after an engine failure and the unsuspecting pilots' time to react. I've haven't seen or heard off an avoid curve predicated for the take off phase only (please someone advise if these charts exist on other types).

Those kind & brave test pilots went up and tested various combinations of height and airspeed from which they could safely pull off an auto & walk away. These were done from various flight regimes i.e. straight & level, climbing, descending etc.

All the H-V diagram is telling you is that if you fly in the shaded area, regardless of what phase of flight it is (and where the collective is sitting), you cannot be assured of pulling off a successful auto (EOL).

So, be aware that flying a constant angle approach could well put you inside the avoid (shaded) area with a combination of height & airspeed that falls in the grey e.g. 20kts @ 40 feet with an armful of collective/pitch as you approach the OGE hover condition, the FM says your rrpm will decay real quick in this condition and your landing will not be assured.

Cheers
J

[Scissorlink]

I have never seen one that says "Recommended landing profile"

[jetA1pilot]

Touché Scissors, good point.

However, in the ICAO testing syllabus, under ex 12 (Transitions) we are required:

To determine that the candidate can achieve smooth and accurate transitions from and to the hover.
Description:
The helicopter will be accelerated to a climb, or decelerated from a descent, safely....while demonstrating awareness of the Height/Velocity Chart profiles.

So, if some manufacturers decide to put in a little helicopter with a dotted line in the HV diagram which is labeled "recommend take off profile", should we draw the conclusion that the HV diagram applies to take off only? Me thinks not

[Benjamin James]

So I take it you have never attended a Robinson safety course jetA1pilot?

[jetA1pilot]

Enjoyed it thoroughly Benjamin - Tim is a gr8 instructor & it was a good course :ok:

[Benjamin James]

Did you miss the part where he explained the H/V curve does not apply to landings at all?

[jetA1pilot]

Nope, he never went down that road.

Did he give you an explanation for that point of view?

A bit off R44 topic but I think worth noting: our Bell twin SOPS: "the HV determination chart limitations at Fig. 2.4 are critical in the event of single engine failure during takeoff, landing, or other operation near the surface. The AVOID area of the chart defines the combinations of airspeed and height above the ground from which safe landing cannot be assured"

Still interested to hear a good explanation why some (incl Tim) think the avoid areas apply to take off only......

[John Eacott]

Bell 412 RFM, Page 62, Sections 2-8, 2-10:


2-8. Take Off

[snip]

During take off, pitch attitude must be adjusted commensurate with power application to prevent entering the AVOID area of the Height-Velocity diagram.

2-10. Descent and Landing

[snip]

Flight Path - Stay clear of AVOID area of Height-velocity diagram (refer to Section 1). I somehow think that despite Mr Robinson's Safety Course instructors dissertation, most helicopters aren't aware of whether they're departing or arriving when it comes to the HV diagram :hmm:

[FH1100 Pilot]

John Eacott:I somehow think that despite Mr Robinson's Safety Course instructors dissertation, most helicopters aren't aware of whether they're departing or arriving when it comes to the HV diagram

John, I must respectfully disagree. I think it makes a big difference to the helicopter whether it is in a full-power climb at 100 feet and 20 knots or a low(er)-power descent with the same parameters.

In the climb you not only have more pitch in the blades, but must overcome the upward motion before you can get that autorotational thingee started. In the descent you're already coming down, and the pole certainly doesn't need to be lowered too much further to transition to the auto.

So yeah, BIG difference as far as the helicopter is concerned.

Let's remember too that the H-V curve is derived at max weight.

On landing, I don't worry much about the H-V curve. As long as I'm not a max gross, and as long as I've got "some" rate of descent going, and as long as I'm not pulling gobs of power, the H-V curve is simply not an issue. And I don't think that's a horribly unsafe mental attitude to have.

I'm not suggesting that pilots can come to an OGE hover at 100 or 200 feet with impunity. And if anyone doesn't want to say that the H-V curve is totally irrelevant to landings, fine, can we at least allow that it is smaller for landings than it would be for takeoff?

[[email protected]]

As was stated earlier, the conditions where the data is taken for the HV curve by the TPs are in straight and level flight with a prescribed delay (longer for mil certification, shorter for civ). Any interpretation of the data for landing or for the climb profiles is exactly that, interpretation.

It seems obvious therefore that in a climb the real HV curve if it were created from real data would be bigger and that one for the approach would be smaller.

But so far as I know only one HV curve is produced for helicopter type certification.

[herman the crab]

As was stated earlier, the conditions where the data is taken for the HV curve by the TPs are in straight and level flight with a prescribed delay (longer for mil certification, shorter for civ).

Are they? What about the left side of the graph at 0 KIAS? There are videos about of the R22 (for eg) being auto from the hover to make the initial HV diagram.

HTC

[John Eacott]

Bob,

I see your point, and it makes sense. But looking at Bell's RFM which directly advise against entering the HV diagram for both take off and landing, and also looking at the R44 HV Diagram (which is what the OP wants!) the only point made by Robinson is a dotted line through their HV diagram marked "recommended take-off profile". JetA1pilot has commented quite well on this.

To interpret that as making the R44 HV diagram not applicable to landings is a long bow, IMHO. Especially for a trainee or low time pilot.

However, the R44 POH does have a fairly well explained landing procedure, which should make the OP's question a moot point: or cause for even more discussion!

Approach and landing

1 Make final approach into wind at lowest practical rate of descent with initial airspeed of 60 knots

2 Reduce airspeed and altitude smoothly to hover. (Be sure rate of descent is less than 300fpmbefore airspeed is reduced below 30 knots.)

3 From hover, lower collective gradually until ground contact.

4 After initial ground contact, lower collective to full down position

[GeorgeMandes]

Through private, commercial and ATP ratings and many recurrent courses at Bell on the 206, 206L and 407, I have been consistently told that the HV curve does not apply to approach/landing as it does to takeoff.

I am also told that the HV curve is developed with a power failure on climb/takeoff and an IMMEDIATE reduction in collective, and in cruise with a one second delay before reducing collective. An approach with a low collective setting, is obviously much different than a high power takeoff where there is much more pitch in the blades. The unanswered question is how much different is the power failure on approach, but we don't have manufacturer's data for that, at least in the 206, 206L and 407.

The Bell 407 RFM, for example, makes specific mention of avoiding the HV curve on takeoff but has no mention of the HV curve for approach/landing. As Bell's former head of their training academy said to folks that showed up and tried to fly a normal approach staying out of the HV curve -- "well, what happens if the engine keeps running," given that an approach flown clear of the HV curve is certainly not normal in any way, and may result in an over torque in the quick stop at the bottom. That doesn't mean that the HV curve should be completely disregarded, and a prudent pilot would try to stay out of the HV curve except as needed to fly a particular maneuver.

George

PS: I am told the reason the Bell 412 has reference to avoiding the HV curve on approach is because the 412 is a part 29 aircraft, and the HV curve is found in the limitations section as opposed to the performance section, as in the 407. I am also told that the HV curve for the 412 is based on loss of an engine, and a successful continued approach, as opposed to an autorotation. As a result, the 412's HV curve looks different than, for example, the 407's HV curve. Since the 412 is designed to lose an engine at any point from takeoff to landing, and be able to continue successfully, where the single engine helicopter's flight is terminating soon after its engine failure, it makes sense why the two types of helicopters would be operated differently.

[SASless]

George......perhaps you might expand upon that statement a bit as I think it is a bit broad otherwise.

Since the 412 is designed to lose an engine at any point from takeoff to landing, and be able to continue successfully

[GeorgeMandes]

Seem like rather than me expanding on this, you should be, since I applied my knowledge of multi-engine fixed wing turbojet operations to what I believe about a 412 operated within a cat A profile. We may have here what President Obama calls "an educable moment," with you doing the educating -- so go right ahead.

[John Eacott]

Seem like rather than me expanding on this, you should be, since I applied my knowledge of multi-engine fixed wing turbojet operations to what I believe about a 412 operated within a cat A profile.

Your original statement was "lose an engine at any point from takeoff to landing, and be able to continue successfully", without the restriction of Cat A/PC1 ops: SASless is quite right to point out that your original was a questionable premise :=

We're maybe getting away from the OP's query, but with the emphasis now on the HV Diagram and its interpretation, this is Agusta's narrative from the A109E RFM. Worth reading as it again applies the HV throughout flight, from TO to landing. A few translation errors, I suspect, from the original Italian but pertinent to the discussion:

HEIGHT - VELOCITY DIAGRAM

The Height - Velocity Diagram enable to establish to establish if, in the event of a single engine failure during takeoff, landing or other operations near the surface, a combination of airspeed and height above ground exists from which a safe single engine landing on a smooth, level and hard surfacecannot be assured (dangerous zone).
The height - Velocity diagram is split in two charts.
Chart A shows the weight values, together with outside air temperature and altitude, at/below which the dangerous zone does not exist. For heavier weights refer to Chart B.
Chart B defines the combinations of height and airspeed to avoid for safe operations.

NOTE
The height - velocity diagram does not define the conditions which assure continued safe flight following an engine failure nor the conditions from which a safe power off landing can be made.A quick check of the RFM's for the BK117, AS365, S76 and S61 all place a requirement to observe the HV for both TO and landing. Single or twin, it (the HV) is something that should not be considered "for take off only" as seems to inferred by some on this thread. A low time pilot must not, IMO, be allowed to develop such a mindset that could become a liability in future flying.

[SASless]

George.....wasn't trying to be rude.....just suggesting an elaboration on what you said might be in order. As in all things.....the details are what kill us.

Firstly, there are many models of the Bell 412.....and they all have different performance based upon the different engines and other Mods.

Add in weights, OAT, take off and landing altitudes, wind, and terrain surface, which might be very different based upon where the aircraft is working, and simple statements such as your are just using too broad a brush.

Take an early model 412.....what most call a "No P" and compare that to the latest greatest 412....call it an EP+ or whatever it is.....and you have two entirely different critters.

[GeorgeMandes]

I didn't take it as rude, and the great thing about a forum such as this, is if you don't fact check each of your statements, there are folks that will help you with that.

The point I was trying to make was that because a part 29 multi-engine helicopter has a height velocity diagram designed around continuing successfully on one engine in its limitation section, and says to avoid the HV area during approach/landing, doesn't suggest that the HV diagram is to be completely avoided on approach by a single engine helicopter such as the 206/206L/407. Further, I believe that trying to fly an approach in a light single that stays completely out of the HV diagram on approach, such as being at 40 knots at 10 feet or the like is a bad idea, just as flying an approach that terminates at an OGE hover at 150 feet is a bad idea.

[jetA1pilot]

FH, George, BJ - good points all. I'll buy into the instructional approach that the avoid curve applies more to the take off phase than landing. However, I still contest that it shouldn't be disregarded for other phases of flight with a broad sweeping "it applies to take off only" brush. Teaching a healthy respect for the HV requirements IMHO is the way to go for 10 hr ab-initio students.

Qwikstop - the reality is that operationally, we regularly fly through the shaded areas of the avoid curve, accepting the risk and mitigating it (statistically if u like) due to the unlikelyhood of the engine actually failing at that point, as somebody said earlier: "what happens if the engine keeps running". Thats where the helo shines in it's versatility - confined LZs, slinging, SAR etc.

The most asked question at the heli-port by the saturday morning spectators is "why don't you helicopter pilots take off & land vertically". Maybe i have to rethink my stock answer of hauling out the HV diagram :hmm:

[SASless]

George,

This article might help a bit......

http://www.stlouishelo.org/The%20H-V%20Diagram%20-%20Bill%20Sanderson%20-%20Rotor%20Magazine%20-%20Spring,%202002.pdf

How does the FAA and the Federal Court look at H/V Diagrams during Certificate ( for you UK folks....License) actions?

http://www.ntsb.gov/alj/O_n_O/docs/AVIATION/3542.PDF

[jetA1pilot]

Thanks SAS - good gen, sums it up & puts it in perspective. Fly in the shaded areas at your peril :uhoh:

George - just to clarify/expand on my earlier post; the 40 till 10 rule of thumb is just that - a guideline and as a ROT it is to be adjusted as needed for the required approach path, primarily according to wind at the LZ.

This technique was carried forward from ex airforce instructors who used it specifically to correct students who were terminating their approaches short of the aiming point in high OGE hovers. The numbers are not as important as the concept of reinforcing the idea of not washing off the speed too early.

As it turns out, where we fly we normally have 10-20 kts of wind on the nose at the training airfield and 40 till 10 works a treat, resulting in a ground speed of around 20 knts with some energy remaining giving good options for EOL landings, t/r troubles etc.

I certainly am not advocating cowboy like quickstop approaches - low & fast is not the intent. However, a fact remains that many students end up high, slow and steep and this is one technique used successfully to get them to fly a safer profile.

QS - ask your instructor to demonstrate a 'normal' approach (not confined, not pinnacle) down a runway to an aiming point, or to an open LZ in your R44 with 15 kts on the nose, make a note of the IAS as you pass through the 20-10 feet agl area. (Ask him to call out when he's at 10-15 feet agl). My guess is (unless he's onto you and he deliberately flies a steep approach), the IAS might be suprisingly close to the 30-40 kt range :)

[Qwikstop]

Here is a video of my last lesson using the constant speed approach -

HG9854ji5T4 (skip to the last minute of vid)

It is definitely not a quickstop - but a gentle transition to a decelerative attitude and then level off to an IGE hover. (BTW, the aerodrome altitude is 250 ft AMSL).

[FH1100 Pilot]

SAS- couple of interesting things from that court case.

1. I see that they only suspended the pilot's ATP. Does this mean that his Private and Commecial were still in force? Or, when you get your ATP suspended does that affect *all* of your certs? Never having had any certificate action (yet!) I wouldn't know.

2. The FAA got him for hovering nearly smack-dab in the middle of the H-V shaded area for the 206. I think it's noteworthy that they took into consideration that he didn't have good forced-landing areas underneath him. I think both of these things are important. Perhaps the FAA would not have gone after him so aggressively if: a) the operation wasn't conducted on a weekday when there were so many people around (to complain); b) if he'd had better forced-landing areas underneath; or c) if he was simply making an approach to a site that required operation in the shaded area.

Point taken, though.

The problem with making approaches that avoid the shaded area of the H-V chart is that helicopters typically don't fly out of airports. I don't know about the rest of you, but in my job a full 80% or more of my landings are to off-airport sites that require something other than a textbook "normal" approach.

And even landing at an airport prevents a normal approach. At an uncontolled field, if I "avoid the flow of fixed-wing traffic," (i.e. don't line up with a runway), I'll usually stay as high as possible so as not to fly low over neighboring houses, etc. This sets me up for a steep, perhaps curved approach to a taxiway or some other spot. At tower-controlled airports, sometimes the tower will say, "Remain clear of all runways," which then necessitates the same thing.

It takes deliberate thought. I "stop" and think to myself, "How am I going to get from here to there while not overflying those houses/hangars/airplanes whatever, and ending up into the wind?" I see a lot of pilots who do not seem to give such things much thought.

The truth is that we *do* infringe on the shaded area in most of our approaches. That's just a fact of life. However, I wish the manufacturers had made the edges of the shaded area "fuzzy" intead of a solid dark, impenetrable line-of-death. Because that is how some pilots interpret it.

I think the best bet is to strike a balance between, "NEVER fly in the shaded area!!" and "The H-V curve does not apply on landing." Do what you've gotta do to get the helicopter there, but don't muck around in the shaded area any more than you have to.

[Shawn Coyle]

From someone who's certified helicopters and taught certification techniques.
A couple of points on the HV curve, in the hope of clearing up some misconceptions. For civil helicopters:

For any helicopter with more than 9 passenger seats, the HV curve is a limitation. If it's a twin engine helicopter, the HV curve is for a single engine failure. Less than 9 passengers, the HV curve is in the performance section.

All HV curves have at least two 'parts'. The part from the low hover point to the knee is flown using takeoff power, but no intervention time from engine failure to pilot corrective action. The part above the 'knee' is flown using power for level flight and a one second intervention on the collective before any action is taken.

For the low hover point - the collective only allowed to be raised. During the HV demonstration, you can't lower the collective and then raise it later.

In summary, the HV curve test conditions are not, repeat not valid for an approach and landing situation. The only place you're going to see an engine failure during the approach and landing situation taken into consideration is for Category A profiles.
And if you want more guidance, look into the Advisory Circulars for Part 27 and Part 29 helicopters.

[Scissorlink]

In summary, the HV curve test conditions are not, repeat not valid for an approach and landing situation

Thank you Shawn :ok:

[Flyting]

Irrespective of how the curve is created, as the mojority of students now a days are mainly PPL levels (with a few going on to become CPs) I will continue to KEEP them out the shaded area for as long as I can...
On a commercial level, it is our jobs to fly in this area a lot of the time, but I'll still keep to one of my first rules learnt...

Stay out of it as long as possible and only go in when neccessary, and then get out again...

There's no need in trying to become a "test pilot" while at work unless you're employed as one.

[GeorgeMandes]

Out of curiosity, how do you teach a normal approach that stays out of the HV curve?

[Flyting]

We taught this profile for approaching:
65-70 kts (auto speed) and descend power (which will vary depending on your weight)
@ 100 ft - 65kts
@ 50 ft - 55kts
@ 10 ft - 40kts
(or there about)
transition back into the hover taxi and then the hover...
This keeps you in a safe flight profile.

The intire approach up until close to losing transition is done keeping the collective quite still and using the cyclic more. Close to when translational lift starts to lessen, start feeding in the collective and the cyclic forward to keep attitude, correct with pedals and hover taxi onto the pad. Remember, this is all done at the airport with lots of open space. Much later on in the training, they will learn about a more steeper approach into a tighter confine, but for this stage of the training, safety is our biggest thing... especially when they start going solo...

[Hughes500]

65 kts at 100 ft, not much thinking time for the 10 hour student there. Think the heli has way too much energy at those sort of speeds. You are bordering into quickstop territory there. Also risk overboosting if there is no wind, you are heavy and you try to stop heli from descending and slowing down that quickly.

[Flyting]

65 kts at 100 ft, not much thinking time for the 10 hour student there
On the contrary, It's all gentle cyclic here to gently slow ROD and speed. The initial descent is steepish, but then it flattens out quite quickly.
You are bordering into quickstop territory there
Not even close
Also risk overboosting if there is no wind
Doesn't matter about the wind. Collective only comes in later around -40kts, and slowly at that, so there is no chance of overboosting. The airspeed drops off as quick as you make it. There is no quickstop effect here.
you are heavy and you try to stop heli from descending and slowing down that quickly
Firstly, we're never that heavy, and again, slow and steady on the controls and the flatish approach...

Give it a try and see tomorrow if you can. Just don't rush it...:=

[Qwikstop]

Have a look at the end of Youtube video I have posted just above. This is a probably a similar approach to that which Flyting has described...

[Hughes500]

Flyting

Sorry that is not a great way of teaching for someone with 10 hours. You are going too quickly at 65 kts ( I presume you mean airspeed here) and 100 ft for a 10 hour pilot. Curious what ROD do you teach at 100 ft ?

[Benjamin James]

Might as well fly a fixed wing with those approaches.

[ralphmalph]

As part of an airtest check the other day I got the pilot to fly some approaches which he has used use in the UK.

These entailed a 10-15 degree nose up attitude to flare off speed at 100' before entering a CAA to a HLS.

The surprising thing was that he had no idea about the effect of a single engine failure at the apex of an aggressive flare.

So when an engine was failed in the flare he was surprised why even after (harshly) putting the nose down (ITW) he would have crashed.

The aviod curve is there as a guide....harsh changes in attitude at the final stages of an approach are I suggest inadvisable.

The Lynx helicopter has a MINSELF of 65 kts in most hot climates....the effect of an engine failure on finals can be catastrophic...

In my mind the sight picture approach works equally as well for SE as well as ME pilots...

Any thoughts appreciated!

Ralph

[GeorgeMandes]

"Sixty five knots at 100 feet on approach."

In 2004, when I was taught to fly helicopters at Bell Helicopter by Wayne Brown, Kevin Brandt, Gary Young and all the fine Bell instructor pilots, a normal approach was described as starting at 500 feet agl and 50 knots. You flew a constant glide path and constant deceleration, ultimately arriving at a slow walk to the low hover. There was no mention of avoiding the HV curve on approach. About a week after starting flight training there, I was soloed, and then sent around the Texas countryside in their Jet Rangers doing what you needed to do for your rotorcraft private pilot rating. Prior to being soloed, I had seen touchdown autorotations from takeoff, climb, cruise and approach.

After leaving Bell, I went straight to Canadian Helicopters for a mountain course. Again, never heard anything about avoiding the HV curve on approach, and in fact learned about a flat disk departure and loaded disk approach. It was drummed in to me that a stabilized approach had a loaded disk, and in that way there were no surprises as to power available at the bottom. On mountain approaches, recce passes were at 40, accelerating to 50 in the course reversal. You lived in the slow speed world, so you could observe ground speed and crab, and the disk better be loaded.

In the years since then, and many visits back to Bell, MD and Canadian Helicopters, I haven't heard anything different on avoiding the HV curve on approach. It generally is a question asked at recurrent, with the correct response being the HV curve does not apply on approach. As I reflected on 65 knots at 100 feet today, it just seemed inconsistent with a normal approach, a steep approach or a standard mountain approach.

In case, I was doing something different and not realizing it, I decided to go test it this afternoon. I was flying a 407 at loaded weight under 4,000 pounds here in Alaska. Since with the FADEC operating, it is almost impossible to get the Nr off 100 per cent, I could do almost any maneuver that I wanted on approach trying to stay out of the HV curve or be at 65 knots at 100 feet.

I flew on and off airport, making approaches to the taxiway, to confined areas and flat open meadows. Even with 5-20 knots of wind, I could not be at 65 KIAS at 100 feet, or stay completely out of the HV curve and be on any semblance of normal, steep or mountain approach. The best thing I can say about 65 KIAS at 100 feet is, it is a great profile for an autorotation.

As long as we are on the topic of "safest final approach," why is it that the "operators" are willing to land down wind with 10 or 15 knots on the tail, when an extra 20 seconds of flight could set them up for an into the wind approach. That got me thinking about the HV curve and wind, and I assumed that surely the HV curve was predicated upon no wind or a headwind. Went and dug out the HV curve for the 407 in the RFM, and there was no mention on the chart of wind. Thought surely it must be in the notes but couldn't find it. Called my buddy at Bell, and he explained to me that the HV curve is predicated upon a hard surface, where a helicopter could slide forever, and doesn't need to be zeroed out. My take away from this is while it isn't real bright to depart or land downwind over a runway, if there is an alternative, it is flat out stupid to depart or land downwind over a surface where you need to zero out your ground contact or topple the ship.

[Hughes500]

As I am bored with this just dug out the flight manual for a 500D
This is the quote ref to height vel diagram
" Airspeed/alt combinatins to be avoided in the event of an engine failure during take-off are shown in the height velocity diagram"

Basically there is no diagram for landing, if there were the curves would be much smaller as you are not climbing, you have more forward energy and the pitch angle of the blades is very low therefore much easier and quicker to get into auto.
As a flight examiner I would be seriously worried ( consider failing on safety grounds) if a ppl was trying to land a heli from 100 ft at 65 kts espically in minimal wind.

[K48]

In answer to the first post.. I say learn the constant angle approach well.. the rest will come later.. The "airfield approach" won't work so well in a field with that hidden cable running across it.:uhoh:

Quote:
I'm sure someone will correct me if I'm wrong, But I do not believe the H/V curve only applies at take off.
It would also apply for example, when ever the aircraft is within the shaded areas, right? which can include low flying (for example hovering at 150 feet). You would not, for example approach vertically from 500 feet with zero airspeed, because if you did, you would be within the shaded areas. Therefore the shaded areas of the H/V curve are to be avoided, including whilst landing.


A H/V curve would be different for different collective settings... I imagine the published h/v curves must apply to a collective setting used at t/o and so would be inherently safe through all flight envelopes including landings (obstacles aside!). But the landing envelope would have a much "free-er" h/v curve if a collective position could be defined... it can't though for obvious reasons...

To take extremes...
Vertical autorotation?
40knots constant angle auto?

Perhaps someone more knowledgable could confirm: Constant angle approaches through the H/V shaded areas would surely allow you to drop into autorotation safely at any point?
The point someone made about not making your helipad from a Constant Angle Approach in the event you need to auto... I believe could also apply to
the low /high speed approach.. imagine the extreme that you are 1 mile out on approach low and fast... your k.e wont save you.
yet I can imagine being able to make the spot from a bit high and slow by dropping into a steep auto.. imagine being way to high... you could hypothetically auto into your pad.... e.g from 2000ft above your oil platform...? Certainly not from the shaded area in the H/v curve with high collective....but with a low collective..?

Someone suggested the safest approach is a perfect auto... a little tounge in cheek I assume... so I will go one further.. :E the safest way of guaranteeing you will make your pad is to be above it.... by vertical auto?

(touch paper lit... standing back :E:})

(just pre-empting the Vortex Ring comebacks... Of course this is not a practical suggestion....!!!) And by the way... I do wonder about the previous suggestions that you "not worry about VRS if you are 'approaching into wind'".. you never know.. e.g the high ground you thought was flat ahead of the Lz blocks the oncoming and wraps the wind in broadside.. or even behind you..... very common... your fast and low approach might catch you out then too......:\:E

[Shawn Coyle]

The HV curve is flown in certification with a maximum of 3 knots of headwind. Never flown with a tailwind (and I wouldn't want to even try...)

[dipperm0]

On the Lynx, during the bad engine MTBF period, we applied, if runway lenght above 1200 ft, 100 ft/ 100 Kt at threshold, then collective fully down, nose up to 10-12 in a slow descent until speed decreases toward O then hover attitude and touch down. It was funny. Kind of horizontal autorotation.

DO

[Gordy]

With all this talk of approach and departure angles, I looked in my files and found this from a post some time ago:

One good way is to stand at the landing point, extend your arm out in front of you to and bend your wrist so that your palm is facing you at eye level. Put the lowest finger on the horizon, parallel with it, and count the number of fingers up until the obstacle is cleared. Each finger is about 3 degrees, so 4 fingers gives you your 12 degrees. You can also do this sitting in the cockpit to judge climb out power requirements.

Another good trick is to extend your left leg to your left side about shoulder width away from your normal standing position. As you shift your weight onto your left leg, violently shift your right leg forward at least 3 feet with your head down. From this position, gently extend your right arm. When fully extended, clench your fist, grit your teeth, look up and extend your middle finger. This is how to greet a fixed wing pilot.

:cool::cool: