Safest final approach
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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
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
Last edited by jetA1pilot; 8th Feb 2010 at 10:22.
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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......
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......
Bell 412 RFM, Page 62, Sections 2-8, 2-10:
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 
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).
[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).
John Eacott:
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?
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
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?
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.
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.
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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).
HTC
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!
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
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
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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.
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.
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
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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.
Originally Posted by 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'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.
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.
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.
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.
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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.
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.
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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
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
Last edited by jetA1pilot; 9th Feb 2010 at 04:53.
George,
This article might help a bit......
http://www.stlouishelo.org/The%20H-V...ng,%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
This article might help a bit......
http://www.stlouishelo.org/The%20H-V...ng,%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
Last edited by SASless; 9th Feb 2010 at 04:51.
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Thanks SAS - good gen, sums it up & puts it in perspective. Fly in the shaded areas at your peril 
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
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
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Here is a video of my last lesson using the constant speed approach -
(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).
(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).
Last edited by Qwikstop; 9th Feb 2010 at 08:34.