Power Check

[jemax]

A question I have asked a few people and no one seems to know the answer.

In a 22 you can power check pre landing by S&L at 50kts, 17"map, plus 6" available hover IGE plus 7" hover OGE, job done.

Are there any equivalent checks for a 44

Ta

[andyhelo]

I was always taught 53kts.

[chester2005]

I agree with 53kts thats what I was shown.

[TiPwEiGhT]

I teach in the R22 and use Vy, full carb heat, staright and level. Would use the same technique in the R44, I'll double check the firgures and post them up, if I remember rightly they are not that much different, I think my one's are for MTOM.

TiP:confused:

[jemax]

Sure it's 53 kts, but what should the power be at that S&L and how much extra for hover IGE and OGE

Tipweight Figures at MTOM would be great.

Also is it different for an Astro, which I tend to fly and Reven 1 or 2

Ta

[vivadavinci]

for both 22 & 44, fly 53 kts straight and level, carb heat cold note map required.

subtract map required from max available map for the conditions, which you checked as part of the start up check list.

if youve got 6in normal approach, 7 in steep approach is possible, 8in full vertical performance.

once youve noted the map at 53kts, pull full power and check there's no rrpm droop to confirm that all the horses that should be there are all pulling their weight.

twas how i was taught!

[jemax]

Viva, that's what I understood for the 22, just wanted to confirm numbers were the same for 44.

[warpig]

i dont do this method because you will have etl. why not just do an oge hover? then you will know for sure if you will have the power to get off the ground.

[Gav500D]

Sure those methods might be alright for a pre PPL pilot pilot, but quite honestly its a waste of time.
Get your stuents or yourself for that matter and start noting your power on lift off in an IGE hover CArb heat off. your power margin is the difference between your hover power and your allowable power.
E.G hovering at 22" max allowable for the days conditions 24.5" power available is 2.5".

Take off.
Cushion creep at full power
normal +1"mp
max proformance +2"mp
vertical take off +3-4mp

Landing
Cushion creep take off zero speed
normal IGE
max proformance 5-6ft hover
vertical OGE

Of course the longer you fly from lift off the more power you will have on landing.
Take into consideration wing strenght and surface from first take as 5kts is usually 1/2"mp

Lets face right from the first take off you should be thinking of what sort of landings and take offs you can do. What if you or your passenger gets sick or you have a warning light come on you should automatically no where you can appoarch into and take off from.
Its looks unprofessional pissing around with a passenger on board fly to 53KTS and then pulling pull. Just pull full allowable power on lift off to see if the needles drop the passengers won't even no you have done.

[last third]

have to have a laugh when folks are talking power and R22 & R44 in the same sentence

:E

[Arm out the window]

Gav, I don't fly the Robbos but even though it's a good idea to check power on lift-off, it doesn't cover the situation when your landing DA is going to be significantly different to that at takeoff - eg going from a sea level pad up into the hills to do a job; the idea that the longer you fly, the more power you will have on landing due to burnt fuel may well not apply.

[jemax]

Thanks for all that,

I had to land heavy, but under MTOM and much sooner than expected in a nasty confined; in which I had to hover OGE to get in.

It would have been useful to do 53kt powers checks rather than OGE hover had I known accurate figures.

Thanks for the figures, I'll experiment and see how they work out.

[the coyote]

Jemax,

You can work out a rule of thumb yourself man.

On a nil wind day, note your power for an IGE hover. Take off and then fly S&L at 500' above that elevation at BROC. Note the difference in the power required.

Then you can say to yourself, S&L at 500' above my anticipated landing DA at BROC, IGE hover power is X amount above what I'm using now.

Experiment a few times, and at different DA's.

But it will certainly get you in the ballpark, and you can apply it to any model of helicopter.

And don't forget the performance charts either.

Comprende?

[warpig]

i agree its not always safe but in a commercial world you cant always do what is "safe" im not saying to act like a loose cannon but to employers, time is money. in my flying i do alot of flying in the hv diagram in a 22. if you dont feel comfortable dont take on the job.

[Arm out the window]

What's the significance of flying the power check at BROC speed?
Can you just pick any speed that takes your fancy and do that each time, or does BROC give a better answer for some reason?

While we're on it, does anyone have such a rule of thumb for the Jet Ranger, eg. fly at speed X, note power required to maintain S&L (hopefully would relate in some way to power required to hover IGE or OGE), as well as some margins for approach / departure.

[the coyote]

Arm out the Window,

Make it anything you like I guess.

BROC in my mind is a good stable speed, and one you are likely to be close to prior to landing or setting up for a recce. It also stands to reason that minor deviations from this speed will not have a huge effect on the power required.

The main point is rather than not have anything to work with until someone tells you some numbers, and/or then blindly use them, think about what you can do to become a safer or more aware pilot.

[[email protected]]

BROC, min drag speed, bucket speed, Vy - whatever you want to call it - as long as you can reasonably accurately fly at the speed that gives you minimum power for level flight (ie at the bottom of the power required curve) then that will give you your available power margin when subtracted from your max power figure. Then all you kneed to know is how much excess power is required for IGE, OGE etc - in the military we tend to operate with a minimum of OGE plus a 5% thrust margin for manoeuvering but that sort of performance is rare in an R22.

I agree that is an excellent habit to note hover Tq/MAP on take off as it a. confirms any pre flight calculations you had made, b. gives you a very good idea of your likely landing performance and c. might indicate an performance problem due to engine damage or the like.

If you are landing away from base then do your power check within 5nm and 500' of the LS to confirm you still have the power available under the local conditions.

[delta3]

crab

fully agree, the reference is taken at the bottom of the power curve.
If that bottom is at 50 or 53 Kts looks a little academic to me, since I believe it will depend on the context (cleaness of rotor, TOW) etc.

If find some time I will check my simulator to predict some BROC speeds on a R44-I in different weight conditions. Of course on a calm day, with some patience one can experiment this for real: try to fly level with the least collective and see what speed you get. The problem doing this is the unstable character of the bottom point: slowing down makes you hit the unstable part of the curve (more power needed when slowing down), so that can be a bit tricky.


d3

[Arm out the window]

I see that flying at min power speed will tell you how much excess power you have at that speed, but what I'm getting at is how does that relate to the hover case any better than any other speed?
For example, there's probably an airspeed you could find for a given type that would require a power equal to that required in the IGE hover, say; or am I barking up the wrong tree?

[TiPwEiGhT]

You're really looking for the greatest power margin available, basically where you have the biggest amount of power to reduce your RoD and stop you hitting the ground.

Lots of power - will possibly allow you to HOGE and the make a vertical descent.

Little power - means you have to make your approach shallower and possibly have to execute a run-on-landing as you do not have sufficient power to stop a higher RoD and possibly not even enough power to maintain HIGE.

Once you have done your power check, always apply that the power you have worked out to have available, the reason for this is to check that you ain't going to overpitch/droop the RRPM... best check it up high then discovering when you are trying to recover from the descent at the bottom of your approach!!!

TiP:}

[Arm out the window]

Maybe I'm being a bit thick, but the way I'm thinking of it is this:

Flying near the pad, it doesn't really mean anything much to me what power I need to fly S&L at BROC speed, but what I'd really like to know is what power I will hover IGE (or OGE for that matter, preferably both) with.
Then I can either use a predicted or allowable maximum power, or even better, pull to one of the limits and see what's available, and apply whatever margins I want to allow for approach/departures.

eg. hypothetical helicopter - say it's TOT limited in the conditions I want to land at, arrive in the area, pull to the limit and check how much Tq available. Fly at my magic speed that equates to IGE (or OGE if I have a speed for that) hover power, then I can say - OK, can pull 97% Tq at the TOT limit, I will need 88% to hover IGE, got a 9% margin which I know is heaps for an angled approach to the IGE hover. Or something along those lines.

Flying at BROC speed doesn't really help with what's going to happen in the hover - or does it??

[the coyote]

Arm out the window,

The speed is not critical for this. What you are doing is applying a rule of thumb that you have worked out previously (or someone else has) to be able to estimate the power required to hover IGE at the DA you are about to land in.

What you want to be able to say to yourself is this:

"This helicopter uses X amount more power to hover IGE in nil wind than it does to fly S&L at my reference speed at 500' above the landing DA." I used BROC as a good reference speed for the reasons previously mentioned.

An example (I've just plucked the numbers out of my head, and notice that 80 Kts is not BROC for the Jetranger):

You have worked out that your Jetranger uses 15% more Torque to hover IGE in nil wind than it does to fly S&L at 80 Kts 500' higher. So you set it up S&L at 80 Kts, 500' above your landing site, and you are using 75% Torque. You then know it will take about 90% to hover IGE. You can then compare that to your maximum power available and determine your margin at the bottom.

If you don't know a rule of thumb, what I am saying in my original post on this is that you can work one out for yourself by experimentation.

[[email protected]]

Armout - the reason for using BROC speed is that someone has bothered to go to the trouble of working out how the power margin available at that speed relates to the power required in the hover ( see Mr Selfish's post for the R22 figures) and therefore what sort of approach you can fly.

Undoubtably you could experiment with different speeds and see how the power relates to the BROC power and maybe come up with a rule of thumb to convert cruise speed power available to hover performance but since you have to come back to 50-60 kts at some stage before landing then that is the time to check your power.

[Arm out the window]

Thanks guys, I just thought that there may have been some theoretical basis for using BROC in that the relationship between that and hover power was predictable, or something along those lines.
I guess next time I think of it I'll look for the relationship between hover power and power used at various speeds, and also see if it's repeatable.