Hover Power + 10%
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From: UK
Hover Power + 10%
For pedants and sad instructor types only.....
A standard transition is hover power plus 10% - If the hover power is 50% for example, does one require 55% (hover + 10% of 50, ie 5) or 60% (hover + 10% of 100, ie 10)?
A standard transition is hover power plus 10% - If the hover power is 50% for example, does one require 55% (hover + 10% of 50, ie 5) or 60% (hover + 10% of 100, ie 10)?
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From: USA
Being pedantic this evening, let me weigh in....
The exact quantity of the standard is subject to questions in its own right, since it is nowhere near 10% for careful procedures where flat approaches and departures can be made. In many types, basic HIGE power can get you off the ground successfully, if a slight dip at 12 knots on takeoff is acceptable.
That all being said, it is 10% of the hover power, so that your 50% power to hover would rule of thumb to 55% as the standard. Each percent equates to a bit of margin above that needed to hover, typically 5 to 10 pounds of extra lift for each extra horsepower. Knowing the calibration of the torque gage is nice, so that you can derive the exact contribution of each percent as equivilent weight or thrust margin.
The exact quantity of the standard is subject to questions in its own right, since it is nowhere near 10% for careful procedures where flat approaches and departures can be made. In many types, basic HIGE power can get you off the ground successfully, if a slight dip at 12 knots on takeoff is acceptable.
That all being said, it is 10% of the hover power, so that your 50% power to hover would rule of thumb to 55% as the standard. Each percent equates to a bit of margin above that needed to hover, typically 5 to 10 pounds of extra lift for each extra horsepower. Knowing the calibration of the torque gage is nice, so that you can derive the exact contribution of each percent as equivilent weight or thrust margin.
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From: EGDC
Letsby, there is frequently confusion about power required for transitions and thrust margins expressed as a percentage.
A HOGE plus 10% thrust margin is basically derived from loading the aircraft up until it only just has enough power to hover OGE and then reducing the AUM by 10% - this gives you an AUM that will allow you to manoeuvre whilst in the OGE hover (some flight manuals specify actual rates of climb or the ability to cope with light turbulence).
The 10% figure that appears in many teaching guides is in fact 10% torque in hand - it is basically a safety measure to highlight that for a normal transition to forward flight (ignoring advanced cushion creep techniques and the like) you need to have available a margin of 10% torque over and above what you are actually pulling in the hover at normal hover height.
So if you are pulling 90% torque in the hover and your maximum available is 100% then you are OK. If your max available (due to other engine limitations like temperature) is reduced to less than 100% when you are using 90% in the hover, you will either need to use a more advanced transition technique or offload pax/freight etc.
Hope this is clearer.
A HOGE plus 10% thrust margin is basically derived from loading the aircraft up until it only just has enough power to hover OGE and then reducing the AUM by 10% - this gives you an AUM that will allow you to manoeuvre whilst in the OGE hover (some flight manuals specify actual rates of climb or the ability to cope with light turbulence).
The 10% figure that appears in many teaching guides is in fact 10% torque in hand - it is basically a safety measure to highlight that for a normal transition to forward flight (ignoring advanced cushion creep techniques and the like) you need to have available a margin of 10% torque over and above what you are actually pulling in the hover at normal hover height.
So if you are pulling 90% torque in the hover and your maximum available is 100% then you are OK. If your max available (due to other engine limitations like temperature) is reduced to less than 100% when you are using 90% in the hover, you will either need to use a more advanced transition technique or offload pax/freight etc.
Hope this is clearer.
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From: Canada
HMMM. Interesting.
I have never considered the 10% to be 10% of the Hover torque for that day...Hover at 60%, T/O Power 66%...rather
Hover at 60%, T/O using 70% (Hover Q + 10%)
As a former CF flight instructor, this is the only standard I and my colleagues have used. In any case, it really is just a value to set so that new pilots (primarily) don't reef in 100%Q for every take-off they do.
Cheers.
I have never considered the 10% to be 10% of the Hover torque for that day...Hover at 60%, T/O Power 66%...rather
Hover at 60%, T/O using 70% (Hover Q + 10%)
As a former CF flight instructor, this is the only standard I and my colleagues have used. In any case, it really is just a value to set so that new pilots (primarily) don't reef in 100%Q for every take-off they do.
Cheers.
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From: Downeast
Well now....what about machines that use "pitch" for power issues? Or...what if you are TOT limited or N1/Ng limited? What numbers do we use now....percentages then get confusing too!
Never mind - Crab has control now!Joined: Apr 2000
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From: EGDC
Letsby, I haven't taught at Wallop since 2001 but I didn't change my nom de prune when I left as I'd got quite attached to it.
The Lynx and Gazelle Flying Instructors Handbooks and Student study guides all refer to hover Tq plus 10% for a normal into wind transition so I'm sure you were teaching the correct technique.
SASless - I don't know what one would use on, say a Puma for example, when there is no tqmeter just a pitch indicator - there must be a Puma QHI who could tell you. If you do have a Tq meter in % then you could equate your N1 or TOT limit to a Tq figure and work backwards from there.
We all know that you can get into forward flight with not much more than hover power but the 10% figure has at least 5 uses:
1. It highlights that to make a standard transition into wind ie one in which you can climb and accelerate you will need a certain amount of power in hand above your hover Tq. (this is for Brit Mil types of transition not CAT A or any clever stuff like that).
2. As WDE says, it stops students trying to overtorque during a transition because they have a specific Tq setting to aim for.
3. It reminds you to use a different transition technique eg cushion creep if you don't have enough power in hand.
4. It is a good ballpark figure for vertical climbs out of confined areas where a towering take off is required.
5. It is also a good ballpark figure for downwind transitions.
The Lynx and Gazelle Flying Instructors Handbooks and Student study guides all refer to hover Tq plus 10% for a normal into wind transition so I'm sure you were teaching the correct technique.
SASless - I don't know what one would use on, say a Puma for example, when there is no tqmeter just a pitch indicator - there must be a Puma QHI who could tell you. If you do have a Tq meter in % then you could equate your N1 or TOT limit to a Tq figure and work backwards from there.
We all know that you can get into forward flight with not much more than hover power but the 10% figure has at least 5 uses:
1. It highlights that to make a standard transition into wind ie one in which you can climb and accelerate you will need a certain amount of power in hand above your hover Tq. (this is for Brit Mil types of transition not CAT A or any clever stuff like that).
2. As WDE says, it stops students trying to overtorque during a transition because they have a specific Tq setting to aim for.
3. It reminds you to use a different transition technique eg cushion creep if you don't have enough power in hand.
4. It is a good ballpark figure for vertical climbs out of confined areas where a towering take off is required.
5. It is also a good ballpark figure for downwind transitions.
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From: UK
Crab - Did you ever fly to Kiel in a 350 with Stumpy leading the show? If so.. I was the good looking one next to Chuck!
I always remembered the instructors' guides saying 'Transition using hover power plus 10%' but I think that's what started the thread...
I always remembered the instructors' guides saying 'Transition using hover power plus 10%' but I think that's what started the thread...
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From: Downeast
also....what happens if you only have hover power...just....and need to go? (...or less than hover power...) Ask any old time Gunship driver about limited power takeoffs...in "B" and "C" model Huey's!
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From: USA
Sasless,
I agree! That +10% rule of thumb would leave about 20% of the aircraft's payload back on the ground, a pretty poor showing!
The guys back in D Troop 1/1 Cav wouldn't have carried a single rocket with that rule.
I think its nice for beginners, but way too conservative for pros.
I agree! That +10% rule of thumb would leave about 20% of the aircraft's payload back on the ground, a pretty poor showing!
The guys back in D Troop 1/1 Cav wouldn't have carried a single rocket with that rule.
I think its nice for beginners, but way too conservative for pros.
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From: spain
Having a flat (nice)surface I to take off. I think it would be rather sad for the operator, customers and pilot to have to leave 1 passenger on the ground on a 206 so that the pilot could hover at 90%with a great smile in his face.All of us that have carried many 2 X45 gallon drums under a 206 we know thats perfectly possible to hover at 100%, and take off at 100 % probably losing a couple of feet between 10-12 knots. The 206 has a good rule of thumb...33lbsXeach 1% of torque.Obviously any tot or n1 limitations would have to be taken into account.
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From: EGDC
Sasless, Nick and Helipedro - the original question was aimed at pedants and instructors so, being both, I gave the standard QHI answer. I suspect that there isn't a training school in existence that doesn't stress that having power in hand to transition is a good thing - but we are talking about training not operations.
In recent years I have seen a definite lack of sensitivity to power limited ops in the military because many front line aircraft are so overpowered - whereas 10 or 20 years ago, many RAF pilots cut their teeth on the Wessex in NI, Hong Kong and Cyprus where being short on power was just a way of life and you learned all the advanced techniques very quickly.
However I have also seen PPL pilots completely ignore their power in the hover and exceed the MAP limit in the transition because they had the 'oh that was only needed during training' mentality.
In recent years I have seen a definite lack of sensitivity to power limited ops in the military because many front line aircraft are so overpowered - whereas 10 or 20 years ago, many RAF pilots cut their teeth on the Wessex in NI, Hong Kong and Cyprus where being short on power was just a way of life and you learned all the advanced techniques very quickly.
However I have also seen PPL pilots completely ignore their power in the hover and exceed the MAP limit in the transition because they had the 'oh that was only needed during training' mentality.
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From: Denver, CO and the GOM
Throughout my training in the 300CB and the R.22 it was a point of pride to very rarely have to add power in the transition. The first time I flew an Enstrom 280C at 5400' pad elevation, I was glad to have developed that habit/skill, as was the aircraft's owner (sitting next to me).
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From: uk
Crab@SAA - Just one more item surely to add to your list is that by using minimum (10%) power this keeps the pitch at the lowest angle to provide a good take-off and if the engine stops then entry into auto is less stressful than if high pitch angles are used.
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From: Norway
Flying the Norwegian oil patch it is required to have power to spare on all helideck take-offs. Maximum torque hovering over the helideck is 15% below the maximum allowed for takeoff.
This is to ensure that you during the takeoff procedure achieve sufficent vertical acceleration to clear the helideck edge in case of engine failure at or after reaching TDP (Takeoff Decision Point).
Examples:
S61N: max. torque for takeoff (5 minutes) is 2 x 103 %
Max. torque allowed while hovering for takeoff is 2 x 88 %.
B214ST: max. torque for takeoff (5 minutes) is 100%. Hovering in takeoff position max. torque 85%.
If torque is higher, weight reduction is required.
Having flown the S61 since -89, and the B214St since -92, this has always made sense. I guess the guys who created this procedure during the pioneering days in Norwgian offshore flying knew their trade.
By the way, these limits hardly ever creates any problems. The ST has acceptable performance for most missions. The S61 would most often be limited by other factors, such as wind, drop-down charts or 50' enroute climb perfomance etc.
This is to ensure that you during the takeoff procedure achieve sufficent vertical acceleration to clear the helideck edge in case of engine failure at or after reaching TDP (Takeoff Decision Point).
Examples:
S61N: max. torque for takeoff (5 minutes) is 2 x 103 %
Max. torque allowed while hovering for takeoff is 2 x 88 %.
B214ST: max. torque for takeoff (5 minutes) is 100%. Hovering in takeoff position max. torque 85%.
If torque is higher, weight reduction is required.
Having flown the S61 since -89, and the B214St since -92, this has always made sense. I guess the guys who created this procedure during the pioneering days in Norwgian offshore flying knew their trade.
By the way, these limits hardly ever creates any problems. The ST has acceptable performance for most missions. The S61 would most often be limited by other factors, such as wind, drop-down charts or 50' enroute climb perfomance etc.
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From: Philadelphia PA
The IGE hover performance charts in all the civil manuals will have a hover height defined. That height is set so that with a fixed collective and a flat surface, you can transition to forward flight without touching the ground as you pass through 10-12 knots of airspeed.
This is to take care of the case where you can hover at that height, but no more than that height, using takeoff power (and not any transients). In that case, you should be able to safely transition to forward flight.
If this isn't one of the things you've been shown or used, it should be. Surprised it's not part of an FAA or CAA flight test.
This is to take care of the case where you can hover at that height, but no more than that height, using takeoff power (and not any transients). In that case, you should be able to safely transition to forward flight.
If this isn't one of the things you've been shown or used, it should be. Surprised it's not part of an FAA or CAA flight test.
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From: Downeast
Shawn,
It would be interesting to see a comparison of the different techniques required on FAA/CAA/MOT/JAR for the same maneuver, normal takeoff from a hover for example. Bet the matrix would be fun to look at and digest. About a year ago I started the thread about Bell 212/412 takeoff profiles from elevated (offshore) helidecks. That was an interesting debate on the "right" method to be used and demonstrated just how diverse the conventional wisdom can be. I suggest, the "official" requirements and philosophy of the licensing authority drives much of that diversity.
What say you?
It would be interesting to see a comparison of the different techniques required on FAA/CAA/MOT/JAR for the same maneuver, normal takeoff from a hover for example. Bet the matrix would be fun to look at and digest. About a year ago I started the thread about Bell 212/412 takeoff profiles from elevated (offshore) helidecks. That was an interesting debate on the "right" method to be used and demonstrated just how diverse the conventional wisdom can be. I suggest, the "official" requirements and philosophy of the licensing authority drives much of that diversity.
What say you?
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From: W'n. USA--full time RV
??? Oh, really? First time I'd heard . . .
Once again, after 17 years flying helicopters, I find that there's a parallel universe of training standards that nobody had told me about. 's OK; I've been sort of following the doctrine without formal introduction (using "some" excess rather than "10%").
I would like to track down the training environment (civil/military, North American/Euro, piston/turbine?) in which this 10% is taught as a standard procedure; I try to stay aware of those parallel universes. In particular, I would be eternally grateful for the titles and authors of training manuals which cite this as a standard procedure, for none of MINE do so. (Civilian R22 toy helicopter background, so sorry.)
AND does anybody know a good, solid, helicopter-specific REASON why so many takeoffs are done at hover power rather than at max power or close to it? The fixed-wing philosophy is FULL power, let's get up high ASAP because the crankshaft is sure to disintegrate within minutes. Helicopters, however, almost universally linger near the ground at minimal power settings, prolonging the exposure to engine failure while low and slow amongst trees and wires and other cuddlies. I can do it OK; I just wonder WHY I'm doing it!
I would like to track down the training environment (civil/military, North American/Euro, piston/turbine?) in which this 10% is taught as a standard procedure; I try to stay aware of those parallel universes. In particular, I would be eternally grateful for the titles and authors of training manuals which cite this as a standard procedure, for none of MINE do so. (Civilian R22 toy helicopter background, so sorry.)
AND does anybody know a good, solid, helicopter-specific REASON why so many takeoffs are done at hover power rather than at max power or close to it? The fixed-wing philosophy is FULL power, let's get up high ASAP because the crankshaft is sure to disintegrate within minutes. Helicopters, however, almost universally linger near the ground at minimal power settings, prolonging the exposure to engine failure while low and slow amongst trees and wires and other cuddlies. I can do it OK; I just wonder WHY I'm doing it!