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R44 power curve

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R44 power curve

Old 20th Jun 2018, 22:34
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R44 power curve

HI All - first post here after reading about a hundred pages of various amazing threads :-)

Is there any place one can obtain a power curve for a R44 II - ideally expressed in MAP inches vs IAS? I know I can probably make one myself in ~2 hours of flying but was wondering if someone has done this already. I did Google it (and searched here) but found nothing.

Why - just trying to better understand the normal power variances between IGE / OGE / S&L at some standard speeds (55, 70, 100, 110kts), etc., to develop quicker / better power margin assessments.

Thanks!
V
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Old 21st Jun 2018, 11:48
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R44 Power Curve
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Old 21st Jun 2018, 13:03
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Thanks TC. I did that. None of the charts are what I am looking for. There is nothing that even says R44. There is nothing that uses MAP on Y axis.
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Old 21st Jun 2018, 22:05
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From my experience, UK, sea level, R44 Raven 2 @ approx 2100lbs;

[email protected] 20", rising to 21" @ 10kts as you come off the ground cushion. 16"@55kts straight and level. 22.5" @115kt.

you can base a curve on that. Roughly add/subtract an inch for every 100lbs
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Old 21st Jun 2018, 22:29
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Excellent - thanks! My sea level is in California San Francisco area :-)

What would you recon your OGE is under those conditions?
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Old 22nd Jun 2018, 21:07
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Originally Posted by valerun View Post
Excellent - thanks! My sea level is in California San Francisco area :-)

What would you recon your OGE is under those conditions?
You can look it up in the flight manual.
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Old 22nd Jun 2018, 23:39
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Hot and Hi - thanks!

Sadly, I can't - this is what my POH has a standard OGE hover ceiling vs gross weight chart (I tried to embed it here but the site doesn't let me add images until I have 10+ posts :-).

I don't know how to get a MAP for OGE at sea level, standard day, at 2100 lbs, from that chart, for example. I know I can OGE at 10,000ft at 2100lbs on a standard day at full throttle (which would be ~19" at that altitude I believe), but I don't know how to convert that to sea level. Perhaps I am missing something...

Thanks!
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Old 23rd Jun 2018, 18:02
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Sounds like on your next flight you'll need a kneeboard, a piece of paper, and a pen.
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Old 23rd Jun 2018, 18:11
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Perhaps I am not understanding this properly.
No one flies on a standard day, it may exist somewhere but it seems more elusive than a positive comment about a robbo.
Any reading will vary depending on density so it's usefulness seems limited and basing a rule of thumb on what you see would need to be in the context of prevailing conditions.
If this was a relevant chart it would be in the flight manual.
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Old 24th Jun 2018, 02:50
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just trying to better understand the normal power variances between IGE / OGE / S&L at some standard speeds (55, 70, 100, 110kts), etc., to develop quicker / better power margin assessments
When flying the Bell UH-1B the military operator had a very nifty means of determining if you had the power available without resorting to charts. You first checked TQ required to fly S & L at 60 knots, and then pulled power until you got rotor droop and noted that TQ. From the difference between the two TQ readings there was a simple gouge as to your capability. The reading obtained would tell if you could HOGE, HIGE, zero/zero, or running landing. Simple and effective, though forget the figures now, too long ago.
If this was a relevant chart it would be in the flight manual
I'm sure that a necessarily experienced engineering/test pilot could develop a similar gouge for a Robbo.
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Old 24th Jun 2018, 07:33
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What is "zero/zero"?
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Old 24th Jun 2018, 08:41
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In Hovering The difference between IGE and OGE is nearly 7 % of power / take of mass lose

This rule is totally independant of the altitude...But you need to read the power in IGE first to know the OGE power.

At the same place and weight :

If you have 20 " IGE, you need 20"+ 7% = 21.4" OGE

If you have 75 % torque IGE, you need 75 %+ 7% =80.25 % OGE

If you have 13° pitch IGE, you will need 13°+ 7% = 14° OGE

If you are at 2000 lbs IGE, for the same power, you have to be only at 2000 - 7 % = 2000- 140 = 1860 lbs OGE

anyway what you use : MAP, torque, pitch degrees, weight the rule is "approximative, but "useful"
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Old 24th Jun 2018, 09:32
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Not really sure I understand the question, but I have a reasonable amount of experience with the R44 around San Francisco. To pick up into a 6' hover generally takes around 21". OGE varies with load, temperature and the aircraft, but in my experience around 22-23". Not sure why it should be different anywhere else in the world! Obviously an OGE hover at sea level isn't strictly possible, unless you potter over to Death Valley.
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Old 24th Jun 2018, 12:03
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Yes, the power between IGE and OGE change, but at the same place, same time and same charge it's always 7% ...And that is really for ALL helicopters..
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Old 24th Jun 2018, 12:28
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Rules of thumb can be quite dangerous if people don't understand the context.
Place, temperature, wind and altitude all change and suddenly 7% is a small drop in a big ocean.
For an aircraft that is notoriously power constrained and involved in too many loss of (insufficient) power accidents there is no substitute for thorough planning.
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Old 24th Jun 2018, 21:55
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Thanks guys - great stuff!

Like I said, the idea is to develop a better understanding of the power difference among various flight regimes.

I specified 'standard day' only to remove the OAT dependency (that many of you correctly noted) from the question. I think I have enough info from POH on performance-vs-OAT dependency to extrapolate from the standard day if needed.

I will also do some flying with a notepad and will post here what I get.

Thanks again.
V
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Old 25th Jun 2018, 09:06
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R22 Butters - a zero/zero is a zero speed landing - you don't come to the hover - it's like a running landing but with no run-on if that makes sense.

The technique can be used in dust/snow (when not power limited) to minimise the downwash effect but can be used (carefully) when you don't have enough power for OGE and are right on the limits for IGE.
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Old 25th Jun 2018, 09:13
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BOBAKAT - I don't think your 7% is accurate (and some of your figures don't add up), the only thing you can say with certainty is that you will need more power to hover OGE than IGE, other than that it is just misleading to try and put rule-of-thumb numbers on it.
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Old 25th Jun 2018, 11:30
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Crab, i don't try to convinct anybody. I learned and used this rule since 1977. I just say the difference between IGE and OGE is always : + 7% of power or : - 7% of weight.
This rule is totally independant of the temperatue, the Pressure, the kind of helicopter or so.

BUT only at the same place , At the same time. Please check for you next flight : Power in IGE and then climb OGE and read the power again...I think you read around +7%
Maybe, check your chart and please look the power diffrence at the same Zp, t° Mass in IGE and OGE ....Maybeyou find 7%
Sure, if you read your power IGE today close to sea level and your power tomorrow at 3000ft OGE this rule is totally false.
BUT it's very useful when you work on the same area and maybe limit the number of "SWP"
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Old 27th Jun 2018, 15:36
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I just checked my current helicopter @ 9000 and 14,000 feet, both times 5,2% difference. At sea level it is a structural limit, iow the same.
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