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Low level autorotation techniques


Rotorhead84
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Everybody gets taught a little bit different. Curious what you guys would do if:

 

 

You were an ag pilot spraying a field at ~20ft AGL and 85kts, fully loaded and you lost the engine.

 

 

You were an ag pilot spraying a field fully loaded and lost your engine during the climbing portion of an ag turn.

 

 

Hoping to learn some new/different stuff.

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Well for the first one... I have never heard of anybody spraying at 85kts it's more like 50 kts. That's right on the edge of the low level/high speed portion of the H/V diagram. As to what to do lower collective to keep your RPM and flare hard enough to keep RPM and bleed off airspeed but not hard enough to balloon up.

 

The second one...

Obviously lower collective start leveling the ship and depending on altitude get a little airspeed or pull hard and fast. These kind of scenarios are hard to explain typing IMHO

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Well for the first one... I have never heard of anybody spraying at 85kts it's more like 50 kts. That's right on the edge of the low level/high speed portion of the H/V diagram. As to what to do lower collective to keep your RPM and flare hard enough to keep RPM and bleed off airspeed but not hard enough to balloon up.

 

The second one...

Obviously lower collective start leveling the ship and depending on altitude get a little airspeed or pull hard and fast. These kind of scenarios are hard to explain typing IMHO

 

Hmmm.

 

 

We spray at 85kts all day long. You wouldnt make any money at 50kts and itd be hard to get all your work done. Not to mention that really isnt enough airspeed for a nice ag turn. Who do you know that flies 50kts and in what airframe? For utility stuff you really cant make money unless you live inside the shaded area of the h/v it seems like.

 

 

As far as the procedures go it seems i was taught similar techniques. Main reason i ask this question is i read about pop up auto rotations, and then i saw the army doing basically run on landings with no flare. Hard to do in a corn field.

Edited by Rotorhead84
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We do row crop work at 60mph (just over 50 kt) and a 3-5 ft height over the crop in 206/oh58. Occasionally we'll have someone put in an order for slow work at 30mph. Not sure about the ag turn speed issues ... 30 mph takes a little finesse, but it is certainly doable, and 60 seems pretty standard, but maybe that is because that is what we do all day. Our external tanks make the ride pretty rough above 80 mph anyway.

 

Tough to train for these types of engine failures, especially at a 3 foot skid height, so first, I try not to think about it, but if it goes bad, I would think instinct is going to put in some aft cyclic to keep from hitting the ground, and if that is successful and I can get some climb, then start dumping collective to get rpm back up and get some energy for the set down... going to be ugly would be my guess.

 

As for the climb, it depends a lot on where in the climb. Higher in the climb, airspeed is down, but I have height, lower in the climb, I have airspeed, but not much height ... use the one you have to get energy back into the rotors and get it on the ground as best as you can.

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By the way, what are you flying at 85 kt, and how are your tanks configured (internal/external, gallons, etc)? Usually, the benefit to helicopter application is the slower speeds and the lower application height to get the chemicals down into the crop and reduce drift ... how do you compete with the fixed wings with those heights and speeds?

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Learn something new everyday! I'm always excited to learn about how other guys do this job!

 

To respond:

 

OH-58's running isolair kits. Tanks under the belly. I can cruise between fields at ~90-95 kts at 80% and the ride is nice and smooth. At only 3-5ft you must be running a pretty narrow swath? We usually fly 10-15 over the canopy of the crop. The rotorwash will take care of most of the drift for you. In 15+ mph winds you're going to get some drift obviously, but you just use common sense and have your driver spot for you so you know how much room you have to work with.

 

Also when I say 85kts that is the average speed. I fly a power setting not an airspeed and barring being forced to fly up/down wind it varies between 80-85kts.

 

How many acres a day do you fly with one ship?

 

We're cheaper, faster and do a much better job than the fixed wing guys. That's how we compete :D

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We have side tanks, so really draggy. Swaths are usually set to 43 ft, but can vary depending on how much we are applying per acre. Varies from 5 gal to 30 gal per acre. If we are flying 60mph, 20 gal work, we can clear 700-800 acres in a day, depending on how many moves and how uniform the fields are.

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We have side tanks, so really draggy. Swaths are usually set to 43 ft, but can vary depending on how much we are applying per acre. Varies from 5 gal to 30 gal per acre. If we are flying 60mph, 20 gal work, we can clear 700-800 acres in a day, depending on how many moves and how uniform the fields are.

 

Oh wow, no wonder you have to fly so slow. Even with flow control you probably can't go faster if you wanted to at those rates. Most of our stuff is 2-5 gallon work. We run 65ft swaths. We usually cover about 2000-2500 acres per helicopter per day during fungicide work.

 

What are you spraying that requires 30 gallon application rates?

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I haven't done a lot of 30g work, but the little I have done is usually fungicide on almond trees, or straight nutrients on cherry trees ... usually tree crops of some sort with lots of leaves to be hit, and they like it done slow (30mph) to make sure the downwash shakes everything down into the trees really well.

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I usually fly at 60 kts for 7-15 gallons /ha work in a 300. if i have to do higher water rates or insecticides in thick canopy i try to slow it to below the magic 40kts, which seems to give the best results. How much can you lift in a kiowa r84?

As for the initial question, we train to pop the collective if we are low ( have time) as you pull back then dump the collective dump the load (if equipped) and good luck with the rest of it! As previously stated it is hard to explain.

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As for the initial question, we train to pop the collective if we are low ( have time) as you pull back then dump the collective dump the load (if equipped) and good luck with the rest of it! As previously stated it is hard to explain.

 

I just want to clarify.. When you pop the collective, what is that... raise or lower?

 

Pull back, (im guessing this is collective) is that flaring, trying to go skids level, or something else?

 

And dumping collective is lowering all the way down, or just a little, or something else?

 

I'm just curious about the technique, and am trying to get a good mental picture of what you do.

 

Note: for the purpose of communication with students (not talking to the OP here), I always try to keep to very specific and universally understood terms. I don't stomp, yank, slam, drop, dump, grab, punch, etc, the controls on a helicopter. Raise, lower, fully lower, reduce by 1", reduce collective as necessary to.....,

 

Specific goals and istructions produce specific results.

 

 

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It's not always possible to quantify or reduce everything to a cookie cutter formula. This technique does not lend itself to being taught by a CFI to a student. It is more of a feel thing after a great amount of time at the controls in that environment.

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by pop i mean raise. just enough with rearward cyclic to get gain in altitude. When i say pull back i meant to say the cyclic. It should be a fluid train of movements as we all know theres not much time in a robbie 22. Then by dump i mean lower the collectiv all the way to the bottom with haste.

 

This is only meant for very low <10ft mid to high range speed eg spraying ops. Where an otherwise immeadiate lowering of the collective would see you rolling down the paddock or when an immeadiate flare would cause a tail strike.

 

The idea is to get the aircraft into a flaring attitude from a low descending situation.

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  • 7 months later...

 

You're going to have to be pretty aggressive on the decel if you're that low. The auto in the video was done from 40 feet AGL.

 

Looks like about 80 feet. How long is the aircraft? It could easily have stood on is stinger twice above the ground as it passes the trees.

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I usually fly at 60 kts for 7-15 gallons /ha work in a 300. if i have to do higher water rates or insecticides in thick canopy i try to slow it to below the magic 40kts, which seems to give the best results. How much can you lift in a kiowa r84?

As for the initial question, we train to pop the collective if we are low ( have time) as you pull back then dump the collective dump the load (if equipped) and good luck with the rest of it! As previously stated it is hard to explain.

 

We fly 80 gallons usually unless it gets really hot.

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Looks like about 80 feet. How long is the aircraft? It could easily have stood on is stinger twice above the ground as it passes the trees.

 

On those lanes you had to stay a bit high then drop down as you cross the road. The standard for the maneuver was 40 feet agl verified by the radar altimeter although the one I got on video could have been higher. Looked pretty similar to all the other ones I watched and flew, though. IIRC 50 feet was the cut off, if you were higher than that they made you go around.

Edited by SBuzzkill
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On those lanes you had to stay a bit high then drop down as you cross the road. The standard for the maneuver was 40 feet agl verified by the radar altimeter although the one I got on video could have been higher. Looked pretty similar to all the other ones I watched and flew, though. IIRC 50 feet was the cut off, if you were higher than that they made you go around.

 

Thanks for the clarification!

 

Good video.

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