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Turb and adjustng forward airspeed


rodrop

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Only cause the weather is a bit iffy here and the winds are starting to gust. I was reading my POH and re-read the statement below:

 

 

Adjust forward airspeed to between 60KIAS and .7 VNE but no lower than 57KIAS, upon inadvertently encountering moderate, severe, or extreme turbulence.

 

So of course I did the math for the R22 and it appears that I should fly between 60 and about 71KIAS. Has everyone calculated this for their aircraft and know it. Or is it an experience thing and you 'just know' :)

Just curious and feel free to correct my math..cause if I am wrong, its my calculator :)

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That would be true for Density Altitudes of less than 3000 ft. Our base elevation is 4500 so I have never had a Vne of 102. On a lot of the summer days we have a Vne around 90 Kias, sometimes less.

 

The way I understand it, if I encounter moderate or greater turbulence on a day like that, I should fly between 60 and 63 Kias. I haven't flown in that kind of turbulence but I'm sure it would be tough to keep the ASI within that range. Different kind of target practice, I suppose.

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According to the placard in the R22 POH, if you happened to be flying at 6000 pressure altitude, and the temperature is 40 C, then your Vne is 77 Kias.

Multiply that by .7 and you get 54.

So in rare cases of very high heat and altitude, 57 Kias is higher than .7 Vne.

 

The only other aircraft I am familiar with is the R44. I have not seen a similar airspeed specification for turbulence in that POH, only for weight, DA, autorotation, Max Continuos Power, and doors-off operations.

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...The only other aircraft I am familiar with is the R44. I have not seen a similar airspeed specification for turbulence in that POH, only for weight, DA, autorotation, Max Continuos Power, and doors-off operations.

 

Its in the Raven II POH, but not the Raven, not sure why, and its "no lower than 60kts" (unlike the R22's 57kts).

 

Keep in mind though, this limitation is only until you have 200tt, 50hrs in type.

 

Personally, I find 70kts feels just fine, at least down here at Sea-level.

:)

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I think the most important thing, is why you should fly THAT airseed. I think if you look through your POH you will find an airspeed that fits in that window (60-71 knots) ;)

 

So what I was trying to get at here was your maneuvering speed. I have not been in an R22 in a while but I beleive the maneuver speed is 65 knots (correct me if I am wrong).

 

In the R44 you should fly between 60-70 knots, should be in the back of your POH under saftey tips :)

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I don't think helicopters have a "maneuvering" speed, (like in the world of fixed-wing)? At least I've never heard of one.

 

The only significance that I know of with regards to 65kts, is that it keeps you clear of the HV Diagram, and sets you up for an Auto.

:)

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I don't think helicopters have a "maneuvering" speed, (like in the world of fixed-wing)? At least I've never heard of one.

 

The only significance that I know of with regards to 65kts, is that it keeps you clear of the HV Diagram, and sets you up for an Auto.

:)

 

That's what I was kind of thinking, goal is to stay out of the HV danger zone :)

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In my opinion the minimum 57 KIAS in turbulence for the 22 is so you don't:

 

1) Exceed loads on the airframe and rotor system.

 

2) Experience rotor rpm fluctuations. The low inertia Robinson system is prone to under and over speeding in turbulence and very gusty winds.

 

3) Suddenly load and unload the rotor system causing excessive flapping which could mast bump or tail chop, exacerbated by 2) and by tail rotor roll in an unloaded rotor.

 

4) Lose ETL and drop out of the sky. If you encounter moderate or severe turbulence, there will possibly be a huge gust spread too. If you're going 40 and hit 25 kt (more or less) gust spreads you might lose ETL and experience dangerous loss of altitude.

 

5) Get thrown around so much you can't avoid PIO or overcontrolling which makes it all worse.

 

I've hit some unexpected bad vertical turbulence in strong winds flying both the 22 and the 44. The challenge is that maintaining 60 kts is a low power setting which allows the rotor rpm to fluctuate more. Had to make a night precautionary landing and wait it out for a day when I hit outflow winds in the Skagit valley and was going up and down 500' on a ferry from Seattle. Steady 25 or 30 kts I don't like but feel safe in the 22, however 15 kt gust spreads are my personal limit.

 

The Astar on the other hand can pretty much fly till passengers barf.

 

The rotor head on Robinson's is the only triple hinge teetering head. Any loss of rotor rpm means less centrifugal force holing the blades rigid from those two extra hinges. Excessive flapping can happen if rotor rpm decays, which combined with control inputs has been catastrophic. Big gusts and turbulence are bad news for constant rotor loading.

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If you have never encountered gusts strong enough to reduce your speed down to these ranges, you should probably grab a CFI and go find a ridegeline and get some experience. Usually you can only control the speed plus or minus 10 knots or more, so any specific number really becomes a "target" speed and not something you can actually maintain.

 

I agree with Whistler in the fact that too low a power setting (problem increased by being lightly loaded) seems unsettling in unloading the rotor and does cause the governor to work overtime trying to maintain rotor RPM.

 

I'm not trying to re-write the POH here, but you can also feel the response of the aircraft based on how turbulent it is and where you feel you have the most control. At sea level and lower altitudes I usually find 60-65 Knots in the R22 and 70-75 Knots in the R44 to be a comfortable airspeed in turbulence.

 

Good article on working around up and downdrafts in the mountain environment here: http://web02.aviationweek.com/aw/generic/story_generic.jsp?channel=bca&id=news/heliops_p02.xml&headline=Helicopters%20in%20Terrain-Induced%20Downdrafts&next=30

 

Some of us without a life that read NTSB reports and FAA incidents may remember the R44 out of San Diego that was in an uncontrolled climb up to around 15000 feet due to a severe updraft. If that pilot was in an R22 we would have found him in orbit!

Edited by Goldy
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If you have never encountered gusts strong enough to reduce your speed down to these ranges, you should probably grab a CFI and go find a ridegeline and get some experience. Usually you can only control the speed plus or minus 10 knots or more, so any specific number really becomes a "target" speed and not something you can actually maintain.

 

I agree with Whistler in the fact that too low a power setting (problem increased by being lightly loaded) seems unsettling in unloading the rotor and does cause the governor to work overtime trying to maintain rotor RPM.

 

I'm not trying to re-write the POH here, but you can also feel the response of the aircraft based on how turbulent it is and where you feel you have the most control. At sea level and lower altitudes I usually find 60-65 Knots in the R22 and 70-75 Knots in the R44 to be a comfortable airspeed in turbulence.

 

Good article on working around up and downdrafts in the mountain environment here: http://web02.aviationweek.com/aw/generic/story_generic.jsp?channel=bca&id=news/heliops_p02.xml&headline=Helicopters%20in%20Terrain-Induced%20Downdrafts&next=30

 

Some of us without a life that read NTSB reports and FAA incidents may remember the R44 out of San Diego that was in an uncontrolled climb up to around 15000 feet due to a severe updraft. If that pilot was in an R22 we would have found him in orbit!

 

That was a good article, thanks

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