OGE Power in Helicopters

Welcome back! I'm Jacob and in this video we go over Out of Ground Effect (OGE) Power. That is, the power required to hover a helicopter OGE as opposed to In Ground Effect (IGE). If you remember from my Airflow at a Hover ( • Airflow at a Hover in ... ) video, it takes more power to hover OGE than IGE. So how can you tell if you have enough power? This video goes over just that.
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OGE is commonly associated with a height of 1 rotor diameter above the ground. That is, if your rotor system is 30’ wide, at about 30’ above the ground the helicopter leaves ground effect and operates OGE. Simply put, this height and anything above it requires more power because the rotor vortices can build much more drastically than if the ground affects them. It’s important to know if you have enough power for this condition prior to getting into to a point where you may need it. Failure to do so frequently results in aircraft accidents / incidents.
Let’s say you want to fly your helicopter from sea level to a helipad in a mountain city at an elevation of 5,000’. You want to pick up 500 lbs. of cargo and bring it back. Prior to departing, every good pilot should do some performance planning to find out power required and power available. Doing this you’ll use weather information to gather temperature and pressure altitude to determine engine power or Max Torque Available (MTA). Then, you’ll compare aircraft weight to determine how much power is required to hover. All of this information will be unique to your aircraft, the mission weight, and the environmental conditions. All of this information is calculated sing your aircraft’s performance charts in the operator’s manual.
For this example I’m making up figures for the sake of easy math and teaching. Let’s say I calculate at sea level with +20 degrees Celsius my aircraft can weigh as much as 7500 lbs. and have OGE power. My aircraft takeoff weight is planned to be 5,000 lbs. MTA for the environmental conditions is 100%. OGE calculates to be 75% and IGE is 65%. Now lets run the numbers for our destination. Max weight for OGE power comes to say 6000 lbs. We plan on weighing 5500 lbs. after refuel and picking up 500 lbs. of cargo. MTA is now 90%, OGE is 85%, and IGE is 75%. The margin between power available and power required shrinks (from 25% difference to 5% difference) as weight and altitude goes up. The power available comes down because there is less oxygen as you climb and engines hit their limiters sooner.
So now I check the numbers. There are 3 easy ways to validate that you have OGE power. 1st: OGE power required should be less than MTA. 2nd: Actual weight is less than max allowed OGE weight. 3rd: IGE is less than the OGE go/nogo weight. By this I mean there’s a 5% margin between OGE and MTA. So if I add that 5% margin to my IGE number I come up with 80%. Thats my go/nogo number for OGE power. If IGE is less than 80%, I have OGE power. If its greater than 80% I won’t.
One last reason this is useful is that you can adjust based on contingencies. Let’s say at arrival they ask if you can carry 800 lbs. of cargo instead of 500 lbs. Looking at the numbers I can bring up to 1000 lbs. of cargo (Max OGE weight minus non-cargo takeoff weight) and still have OGE power. But if they want me to pick up 1300 lbs. I would have to say no or come up with a takeoff than didn’t require OGE power.
So that’s how you pre-plan power. What if you’re flying right at the edge of OGE power and need a little more lift to just get up and going? That is, OGE power is right at MTA. Here are a few tips:
1. In a neutral wind condition, you can do a spiral takeoff by applying right pedal for counter-clockwise rotating rotor systems (left pedal for CW). This reduces tail rotor anti torque and in essence gives power back to the main rotor by reducing pitch/drag in the tail rotor. Warning: Never do this in high winds in your Loss of Tail Rotor Effectiveness (LTE) regions or you could have an uncontrolled spin (My LTE video here ( • Loss of Tail Rotor Eff... ).
2. Hunt for the winds. Relax on the pedals and let the aircraft weathervane into the wind. Once you find it, translational lift slowly takes effect and the helicopter climbs more efficiently.
3. Springboard takeoff. Starting from a hover, slightly reduced collective then rapidly pull up collective to MTA/OGE power. The aircraft will momentarily descend and create a high pressure cushion underneath which acts like a springboard to push the helicopter up. The springboard is gives the aircraft extra inertia and is most effective in confined areas where the air cannot escape as easily under the rotor system.
By using one or more of these techniques you can squeak out just a little bit ore lift on your OGE takeoffs. As always, I’m Jacob. Safe flying.

[@djameshayes]

I am an old guy who flew Hueys in Vietnam. I love all your videos! Makes me wish I could 'strap' a Huey on again and do some flying.

[@helicopterlessonsin10minut10]

I wish I could strap into a Huey also. I grew up around them but they were out of the fleet when I became a pilot. It was an amazing and iconic bird!

[@djameshayes]

Your videos reflect strongly on your professionalism and passion for flying. Great Job!!!

[@rgardner922]

Glad you explained the techniques on creating slightly more performance for OGE takeoffs.

[@georgedemeris]

Watched your videos on the way in to work and home again for a few weeks leading up to taking the SIFT. Ended up with a 65! These were a huge help, thank you!

[@peteyyy2]

Thanks for the video brother.

[@OculusQuestFun]

I've talked about how I'm most interested in the Mosquito Helicopter (XEL), so not every video is pertinent to me, but know that I watch then all.

[@harishkrishnachaitanya8691]

Hi, Extremely helpful videos Can you please make a video on Power Availability and requirements with special emphasis on Range and Endurance. Density altitude and problems at high altitude...

[@mariotadeu1190]

muito bom

[@CC-bq7wk]

Would you do a video using charts??

[@OculusQuestFun]

Those intros man...nice. and thanks for the Out Of Ground Effect video. Super helpful.

[@rszkodzi]

Jacob, the springboard and spiral tips to gain a bit more OGE during takeoff are really interesting. However, doesn't that end at the momemt you reach OGE, so in effect you can get to OGE, but once there, you are still underpowered. I assume the followup technique is to transition to ETL to gain more lift and then begin working your way down the mountainside to thicker air where you no longer have a small variable. Can you explain?

[@jaafarmahmood6430]

Is the angle of attack in OGE same in IGE? Can you explain that Jacob … much appreciate

[@lennertpraet9357]

Is it posssible to calculate the HOGE ande the HIGE without the charts, if you know the parameters?

[@daycrumpler]

I'm surprised you left out the other option to do a rolling take off if you have a flat area or an aircraft on wheels? Where you have ground run and once you pick up enough speed and the blades experience ETL you now have sufficient lift to climb. Great video nonetheless!

[@helicopterlessonsin10minut10]

I left that out because that would be a takeoff that doesn’t require OGE power. Getting through ETL first is always the preferred technique. But if it’s not in the options based on the takeoff area, these techniques can help boost your normal OGE takeoff.

[@dakotarager6154]

Hey Jacob, I'm very interested to learn more about the springboard takeoff and how the aerodynamics of it work. I can't seem to find anything by looking it up online. Do you have any materials or sites that explain it or another name it is known by? Thanks a lot and thanks for the videos.

[@helicopterlessonsin10minut10]

I don’t recall ever seeing a written reference. It’s something that’s been passed around the helicopter pilot community, especially in aircraft that frequently don’t have much OGE power.

[@australianchad6450]

Nice job mate Need a new sharpie haha

[@CC-bq7wk]

A video using OGE and IGE charts

[@cillersbadass7590]

hey I´ve seen you make really good explanations of helicopters, could you tell me what the advantages of having a rotor design like the Ka50&52 Heli vs the the Mi28 (no back tail rotor vs having one) I am looking forward to hearing from you!!!

[@helicopterlessonsin10minut10]

Having the stacked rotors like the KA50 is what’s called a coaxial design. By spinning opposite directions, it takes away the need for the tail rotor because they counteract each others’ torque effect. This allows more power to go to the main rotor which can increase its overall lift. This design also allows for a faster top speed because the rotors balance out each other when it comes to retreating blade stall. But this system is generally more complex and expensive to design, build, and maintain. The Mi28 type system is easier and cheaper to mass produce and more of a legacy type design. I’d say it really comes down to budget and what someone needs a helicopter to do. As far as militaries, how many helicopters could you get on a certain budget makes a big difference. Great question.

[@cillersbadass7590]

@@helicopterlessonsin10minut10 thank you. Do you know why we in the western world don't have something like that? I mean the US spend the most money out of all nations for it's military And does the h-47 Chinook uses the same art of travel or is this a way different one? Thx for answering!

[@helicopterlessonsin10minut10]

I think it came down to costs. Coaxial design wasn’t prevalent during the time the Army bought the Blackhawk, Apache, Kiowa, or Chinook. But it’s growing in presence now a coaxial design is actually in the running for one of the Army’s next aircraft purchases to modernize the fleet. To answer your second question, yes the chinook is more similar to the coaxial design but it still hasn’t it’s differences with the rotors being in tandem.

[@DrunkHog]

Now here come the questions: How do the pedals make such a helicotper like the Ka52 turn? My assupmption would be that they modify the pitch collectively on ONE of the rotors. Or both?? IE: I wanna turn right, they'll lower the pitch on the clockwise rotor and raise the one that spins CCW, to increase the counter-torque. That would probably also require some input from the requlator (IF the subsequent DEcrease of torque on ONE rotor with the INcrease on the other do not cancel each other out). But is that it? Is that how it works?

[@helicopterlessonsin10minut10]

You’re on point. You’d have to change the collective pitch of one of the main rotors to turn or yaw right or left

[@OculusQuestFun]

Is there anything I can do to support your channel? Merch, patreon, channel membership? Anything like that? Thanks.

[@helicopterlessonsin10minut10]

I’ve got merch listed and also a contribution link in the about section with a PayPal link if you want to buy me a beer or coffee lol. I appreciate the support!

[@OculusQuestFun]

@@helicopterlessonsin10minut10 Very good. Thank you.

[@PLISNO]

I like your videos a lot, but I have a question: when someone makes an "spiral takeoff" aren´t they actually decreasing the "Rotor RPM" in relationship to the airflow? Example when you make a 2RPM spiral T.O. isn´t that RPM going to be subtracted from the main rotor (not in the gage, off course), so you end up with 2RPM less, thus decreasing the actual rotor RMP and increasing the conning angle? I fly Sikorsky S-76 in the offshore industry, sometimes when we are near or at max gross weight with little or no headwind, I feel it´s easier to T.O. by pulling the collective gradually, but with no hesitation, from full down to max takeoff power, being preppare to abort if it fails to leave the ground at 90%Q or have any tendency to a dinamic rollover. This way we are able to takeoff vertically until the 20ft decision point and can fly away, that would be very difficult otherwise. Best regards from Brazil and keep up the good work!

[@helicopterlessonsin10minut10]

Interesting. I’d never thought of that. But with rotor systems turning generally over 300 RPM, the 1-2 RPM of the pedal turn would account for only a fraction of a percent of rotor RPM as a difference. However, offloading part of the tail rotor requirement for a takeoff by using a spiral can significantly improve climb performance by at least a few percentage of torque. From experience I’ve seen it to be more of an increase in climb rate using the spiral technique. Great point through!

[@truckerray7533]

Is your onboard fuel weight a cosideration of somekind in these type of factors as well??? Can ya perform a good "springboard" lift off in an wide open accessed area as well???

[@helicopterlessonsin10minut10]

Yeah fuel, cargo, passengers, and everything else is considered. You’re planning on total aircraft weight at takeoff. And yes you can do this type of springboard takeoff anywhere. Although it’s not as much of a boost in open areas.

[@truckerray7533]

@@helicopterlessonsin10minut10 Okay, cool. Thankya for the reply back. Do ya have a video anywhere in the explanation of a wheeled helo performing ground taxis & rolls??? I try to watch the main rotor blades on these type helos & looks like there's enough positive pitch in the blades/"rotor disc area" to perform the aircraft ground movent but yet not so much for the birds to leave the ground until pilot command imputs says so! How do ya know the right balance & feel between the rolling taxis without the actually aircraft leaving the ground just yet???

[@helicopterlessonsin10minut10]

For wheeled aircraft it’s usually outlined in an operators manual or training manual how much power to use for different maneuvers. It takes very little pitch to actually ground taxi wheeler aircraft. For rolling takeoffs you could use something like hover power minus 10% and it should get you rolling just fine.

[@truckerray7533]

@@helicopterlessonsin10minut10 Okay. . . . . during the taxiing ground roll, im guessing the pilots are applying a touch of "forward" cyclic imput. . . . .yes???

[@helicopterlessonsin10minut10]

That’s correct. And for a rolling takeoff you’re generally keeping an accelerative attitude and level fuselage without allowing the nose to tip too far forward which could risk front flipping.

[@biblewaytolive]

To fast and complicated needs to make three out of one video