Flying at High Density Altitude

[Edd Weninger]

Has anyone solved the problem of flying at density altitudes of 8,000 - 9,000 feet?

I live in central AZ at 6,650 feet above sea level. When it is warm, the density altitude can easily reach 9,000 feet. While the electric motors do not lose efficiency, the props do. So total vertical thrust is reduced. While my P2V is capable of take off and hover, there is not much thrust in reserve to cope with the most minor wind gusts.

At times, I've jumped in to add more power than the flight software provides but once the aircraft is settling, it gets into a fight regime known as "settling in your own downwash". It is not a severe crash as you still have vertical thrust, but you do end up on the ground (if you miss any other obstacles).

I've got the largest carbon props that fit, which help, but......

I'm thinking of making motor shaft extensions for two of the motors which would an overlap of blade tips for larger diameter props.

So, what shop has the best selection of props, pitch and diameter ??

Or higher power motors ??

Anyone approached the problem in a different way ??

Thx,

 

[RoyVa]

Research and users have found that the original props are best as they were engineered with the proper flex and pitch. Carbon fiber is to stiff. May want to look at the upgraded motors if it's the older phantom.

 

[Clampit]

I would always stay with stock props but that's my opinion I've heard to many horror stories about 3rd party props let alone CF ones.

Would not like to see ya crash cos of using the wrong gear but that's up to you

 

[IflyinWY]

Hey Edd, WELCOME TO THE PARTY

I've done a fair amount of flying at 5 to 8,000 MSL. The Bighorn mountain range is a great place for flying. I am flying the FC40 and the P1.

The best setup I have found is to keep Gross Weight to a minimum and use DJI 9540 props.

I can do alright, even in 15 to 25 mph winds, which are never without gusts. I have to agree with RoyVa and Porky. I don't believe those CF props are doing you any favors.

How much does your bird weigh and what does DJI day the MAX Weight should be?

Settling with power is often referred to as VRS. I encounter it often when the bird is heavily loaded. Lateral movement in any direction helps you to avoid VRS. Keep in mind which way the air mass is moving when you decide to move laterally.

Overlapping props may not help because of the loss of efficiency of the lower level prop tips. Your motors may run out of Umph to spin the props fast enough too. I am interested though.

Helpful links in my signature, if you're interested.

 

[Edd Weninger]

Thanks. I'll do some testing to measure what the vertical thrust is with both prop types. IIRC, going to the carbon props did seem to work better when I first got them. But it was some time ago.

Was hoping to get some aerial footage at our upcoming EAA fly-in, but no sense putting shiney airplanes at risk.

 

[IflyinWY]

Cool idea getting some aerial at an EAA fly-in, but when could you fly? If it's a good size show, there will be stuff flying most all the time.

Ya might end up being the "Turd in the punchbowl"...

 

[kenundrum]

Remember that yaw is controlled mostly by managing engine torque. That's why you may occasionally notice a dip to one side when doing extremely fast turning since some of the motors have to spin slower and you lose some lift. Since all the motors are fully independent, i doubt it would be a good idea to allow for interference in the props. They would likely smack into each other at some point. Also- with props not in the same plane, you end up with a lopsided center of thrust that the flight controller would try to compensate for as well as reduced efficiency in the lower set of props as they flow through the turbulence of the top set.

 

[IflyinWY]

Remember that yaw is controlled mostly by managing engine torque. That's why you may occasionally notice a dip to one side when doing extremely fast turning since some of the motors have to spin slower and you lose some lift. Since all the motors are fully independent, i doubt it would be a good idea to allow for interference in the props. They would likely smack into each other at some point. Also- with props not in the same plane, you end up with a lopsided center of thrust that the flight controller would try to compensate for as well as reduced efficiency in the lower set of props as they flow through the turbulence of the top set.

Yep.

If it's possible for the props to smack each other, it's just a matter of time.

I am a big, one of the biggest fans of "As large a prop as you can get" but the overlapping thing doesn't sound so good.

There are arm extensions which would allow you to use larger props, but where is the power going to come from, to spin them?

 

[Edd Weninger]

I plan to measure the vertical thrust I can achieve at my density altitude with both the carbon props and the Phantom 9450. I didn't have a fresh set of 9450s so have ordered some.

Temp today is 74F so the density altitude is only 8,600 ft.

When I do the testing, I'll observe the prop blade flex. So, if I do try the overlapping scheme (machining some motor shaft extensions for 2 motors) I can keep them far enough apart.

If more power is needed there is the t-power option. However, the motors do not lose efficiency at altitude, so recovering the prop blade efficiency in the less dense air should not require more power. We'll see.

Cheers,

 

[IflyinWY]

I do believe there are a very small percentage of folks interested in our thoughts. Most never get to where the density altitude has any effect on their flights. When they travel to higher elevations and get short flight times, I think they attribute it to a battery not being fully charged or some other issue.

I've done some very crude testing on the bench.
http://www.phantompilots.com/threads/either-im-a-genius-or-an-idiot.42519/#post-390925

 

[Cris A.]

Most of my flying is at 8,500 AMSL or higher here in the mountains of Colorado, some of it on relatively hot days (80s) when the density altitude is upwards of 11,000 feet. No issues observed so far, even in a fair wind. I really can't tell the difference between flying here and at lower elevations.

I wonder if you problem isn't more weight than just density altitude by itself.

Years ago, I took off in a Grumman single in Amarillo, Texas (3,700' AMSL) on a 90 degree day with three aboard and half tanks -- well below maximum gross weight. I pretty much had to fly in ground effect across ranch land and farm fields, dodging fence posts and power lines until I could get over Palo Duro Canyon and take advantage of some southwesterly winds that upsloped on the canyon walls and put some air under my wings so I could actually turn around and head back to the airport. That was a lesson I have never forgotten!

 

[Edd Weninger]

I tested two sets of props to measure maximum vertical thrust achieved by my Phantom 2 Vision at my density altitude.

I live at an Airpark (AZ82) located at an elevation of 6,650 feet above sea level. Air at this altitude is considerably less dense than at sea level, and when the air temperature increases above Standard Atmospheric conditions is becomes even less dense. For aviation purposes the term Density Altitude is used for pilots to gauge the performance of their aircraft. Normally aspirated engines lose power output, and aerodynamic surfaces lose effectiveness. This is true for full-size and scaled aircraft, including my P2V.

I posted here of my P2V hovering issues here, it was suggested the standard DJI plastic props were better than the carbon props I was flying with, so I decided to test them, and at the same time determine the reserve vertical thrust obtained by the P2V.

My P2V is stock but for the addition of prop guards. It weighs 1,251 gm. with DJI 9450 props, and weighs 1,260 gm. with carbon props. I tie-wrapped the P2V to a dumbbell weight of 3,293 gm.

The P2V and weight were placed on a digital scale capable of weight measurements up to 7,000 gm. with a resolution of 0.1 gm. With the weighted P2V on the scale, the start weight was recorded. The scale reading was recorded at full thrust 3 times and the readings averaged. This was done for both prop sets.


Atmospheric conditions: Temp 71F, Baro 30.24, R.H. 44%, Density Alt. 8,100 ft.

+++++++++++++++++++++++++++++++++++++++++++++++++++++

Results:

9450s
Start wgt.----------->4,450 gm.
Full thrust wgt.---->2,590 gm.
Vertical thrust----->1,950 gm.
P2V wgt.---- ------>1,251 gm.
Reserve thrust-----> 703 gm. 56%

Carbon
Start wgt.----------->4,553 gm.
Full thrust wgt.---->2,720 gm.
Vertical thrust----->1,833 gm.
P2V wgt.---- ------>1,260 gm.
Reserve thrust-----> 573 gm. 45%

So, surprisingly, the carbon props weigh a bit more than the 9450s and are a tad less efficient. They produce 11% less reserve thrust, which doesn’t sound like a large amount, but maybe the algorithms in the stability augmentation system are more affected than one might think.

I’ll fly the new props a bit and see if I can discern a difference. If they’re not significantly better, I might have to spring for the higher power motors.

Anyone ever made measurements of the sea level thrust? I had no issues in SoCal.

Thx,

 

[Edd Weninger]

Chris,

Have a similar recollection flying my 125 Hp Swift out of Grand Canyon Airport with a new girl friend. Flew up in the morning, had lunch and wandered around. Flew out about 4:00 pm. Luckily, the ground drops away flying to the south west, so while we didn't climb, we kept getting higher.

 

[IflyinWY]

@Edd Weninger
**** nice job testing the props.
Including the conditions makes all the difference, in my mind.

I'm surprised the CF props were outperformed by the DJI 9450s. It's a pleasant surprise though. I'm not a fan of spinning razor blades...

It would be nice to hear from someone @ sea level who would also include the pertinent info.

If I'm not mistaken, your Swift can fly almost as slow as the Phantom can go fast. Any thoughts about getting some air to air video? Sure would be sweet to see. Heck I'd settle for aerial of the Swift parked.

 

[atl_quad]

I'm new to the forum, but have been lurking around in the shadows on here for a few months now. I referenced all of the high altitude flying threads before heading on vacation to Colorado to fly while backpacking this fall. Very useful information and I can now confirm that the stock Phantom 3 handles very well in thin air. For my first post, here's a look at the flights I managed to get in between all the gusty wind between 10,500 - 13,500' ASL. Although the Inspire would have handled the wind better, the Phantom 3 is really the only option if you want to carry it into the backcountry with all the other necessary multi-day backpacking equipment. I also found that hand launching is usually necessary in the alpine... something that doesn't look very feasible with the Inspire. Hopefully I'll be able to contribute more useful material to this group in the future, but for now here's a link to the video. vimeo.com/upthink/colorado

 

[FatPanel]

I fly high altitude in Colorado, often at 7500 to 12000' with my P2V+v3. I balance my blades, get it in the air and go...

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[Aerocet]

Hi
I am a new owner of a Phantom 4.
Never flown a drone before. This little bird flys like an angel.
Durinng my trip to Bolivia I have flown my drone at elevation of 4,800 meters in wind gusting to 20 knts. with the stock propellers.
It performeecflawlessly.
Great bird

 

[Othan1]

Yeah, what? I just got back from flying at 10,000 feet in Colorado at 96-110 degrees with no issues and I have the DJI carbon fiber props.

I usually fly it in San Diego so it seems to handle negative altitude as well as thousands of feet very well.

 

[jsallee1963]

For all phantom 3 Professional owners living at high altitude. I live in Denver Colorado and the stock and carbon DJI props. They work fine but I'm always looking for the best prop for 5000 to 10,000+ flight that gives me the best flying times and least strain in the motors.
My favorite props by far are made by Aeronaut because of its large surface area, lightweight pure carbon material and quality. So far I've purchased four sets and put them on my du-bro balancer without having to adjust one prop.
Before Aeronaut came out with a CF prop for the P3P I had three drones stolen (still pissed!) and I still had my Aeronaut props for my Blade Chroma 4K. One day I realized they looked similar in shaft size as my P3P and sure enough they fit, but at 10x5 they were 1/2 inch too long. I made a crude but snug template for my band saw to cut the tips down then balanced them. I used a dab of loctite since they were metal centered props.

I was stunned at the performance of the now 9.5x5 Aeronaut props! At 6500 feet AGL I averaged 16.5 feet per second vertical climb and 54.5 mph flat out speed! I schooled several Phantom four's and we both have the same motors. Aeronaut has since come out with P3P CF props 9.5x4.5 and I bought a set. They worked great but the secret is in the pitch of the blade. Not to mention they are the quietest props I've ever heard unlike DJI's being the loudest I've ever heard. As far as battery life per flight I haven't noticed any loss compared to stock props but I've been flying it pretty hard testing it's performance. I will do an air time test this week weather permitting.
I wrote to Aeronaut and they are very interested in seeing the video I'm making and may consider a high altitude line of props for DJI and Yuneec. Until then you high altitude P3P owners buy the Chroma 10x5 Chroma props and have them shortened to 9.5 width. If you don't have a band saw find a machine shop or go to a high school wood shop. It's critical to cut with a high speed fine tooth blade.
I will be making a video this week so you can see for yourself that Aeronaut makes by far the best lightweight carbon fiber prop......period! I'm taking it the Spanish Peaks area in Colorado tomorrow at 10,000 foot elevation. I will return with the results later this week.
Any Phantom pilots living at the same altitudes have any tips for me I would sure appreciate it since I'm new to the forums. I wish DJI would come out with wider stance landing gear like the Blade Chroma! I hand grab mine but there are times I want to land away from my take off point! The black attachments on eBay look like look cheap but charge the same price as the DJI P2 wider stance gear. Hey DJI is this your way of making more money when people crash and have to send it in to you? You know it's a terrible design and looks so out of place for such a beautiful machine! You did a little better on the P-4 skids but they are also easy to tip over. I have friends with CAD capability and I may just start business improving those parts that should have been corrected and new ideas from the feedback of others.
Sorry about the "Rant" my friend's but I'll bet some of you feel the same!
Thank you and fly safe!
PS. You can order the Aeronaut props through "Carolina Dronz"

 

[Alex Baxter]

And did you ever get the props off after the dab of loctite? [emoji123]

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