Weird Air

[ZipItyDoDa]

Weird Monday flying, May 22, 2006.
Beautiful day for flying high of 76, winds light and variable all day. Went out around 5pm. I have a HHF with 503 single carb, PD 500. I had a 150lb passenger and the takeoff was nice & smooth. (Normal)
Kept on climbing until around 80-100 feet hit some turbulence. So I eased off the throttle to try and stay below it. Now we are above 2 farm fields that are both 3/4 of a mile square. I make a slow turn and try heading out and we have been coming down very slowly and there are lines ahead, so I go to full power to climb to a safe altitude over them, but the PPC is not climbing, its actually slowly sinking. So I turn west to give me time to start climbing, these fields are HUGE. But again its slowly sinking, at full power! I fly along a long ways and then decide I'll try turning into the southerly wind (which has been shifting some) to try to get some climb out of this thing, so I make a slow turn south.
Now separating these two fields is a regular field fence and I am heading toward it and still not climbing. And now I am so low as to not be SURE I can make it over this fence. So I ever so gently push the left rudder bar to try going back east, when I lose the rest of my lift. I quickly decided to flare and cut power to put it down before getting to the fence.

Unbelievable!! 6 years and 600+ hours of flying and I have never had something like this happen. I have had the cart overweight and experienced something like this, but never under these conditions. These fields are huge and none of the maneuvers were done in haste, except the last touchdown.

Well I got off, turned the cart into the east and setup again and we took off. Again with slow climb and then the wind caught and we gained altitude. But it was still a bit rough up there. I thought it might be a transition between two air masses, so I kept climbing to try to get out of it, but it got worse. So I cut the ride short and went back to the field and made a very soft perfect landing. (I told the passenger that this one would be better than the last one, hitting corn rows sideways!)

Then as we are packing chutes a guy we know with a fixed wing Challenger flies by and then turns to land. He came down, lost lift and bent a landing gear. He hadn't planned on landing. He said he just landed to ask us if we thought it was strange out flying today. He had been on a full size private landing strip and he was saying that it took him twice the distance to get up as usual and thought it was strange. So I told him my sad story. He managed to straighten the gear up and bit and takeoff ok. (Not a problem with altitude density.)

I'll be checking my machine over good, but doubt that I'll find any cause from that. Just a weird day for flying I guess.

[Skypilot]

Hi Zip

Your description sounds like you may have been experiencing some form of Microburst. Were the fields you were over dark colored compared to those adjacent to them? Do you know what the density altitude was? Were there any clouds in the area? Did your ground speed seem higher than normal?

[ZipItyDoDa]

Hi ZipYour description sounds like you may have been experiencing some form of Microburst. Were the fields you were over dark colored compared to those adjacent to them? Do you know what the density altitude was? Were there any clouds in the area? Did your ground speed seem higher than normal?

These fields were fresh turned, but so are all the surrounding ones. Plus others were having the same weirdness miles away. I don't know what the altitude density was at the time, but I have experienced it many times. And this didn't feel like it as I was taking off, but was similar once I was in the air and had to fight for altitude. Can there be altitude density problems in layers of air???
There weren't any clouds and ground speed seemed normal.
I have gone out one other time when it looked good for flying and then took off and had it feel weird. But no passenger. I turned back and landed, packed up and called it a day. But these are the only two days in my years of flying that have felt strange like that.
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[Skypilot]

My instructor, JD Rexroad told me of a simular incident that happened to him a couple of years ago with his PPG. A group of guys were flying from a field near Omaha. It was a summer afternoon and he helped everyone else get launched and no one seemed to have any problems. When he launched he got off the ground OK but said he could not climb and ended up having to land in the next field (to keep from hitting some trees), to make things worse where he landed there were Bee hives and he ended up being attacked by the Bees. He said the wind was light at the time. He still dosen't know what caused his problem.

There is one incident in the data base where someone had to much pitch in his prop and it was partially stalling until his speed reached 30 MPH or so and it caused him to crash after takeoff because he couldn't gain enough speed to get his prop out of the stall range. Any chance you might have had something like that happening to you?

[kilowatt]

Good Evening,

Density Altitude is simply a comparison of a volume air to the International Standard Atmosphere (59 degrees fahrenheit, with a pressure of 29.92 inches of mercury at sea level).

Air density is affected by temperature and pressure and altitude.

Air density varies with temperature (typically higher temps, lower density).

Air density varies with pressure. (typically higher pressure, higher density).

Air density varies with altitude. (typically higher altitude, lower density).

In basic terms; it's the altitude that the engine and aircraft "think" they are flying at. We all know that a given volume of air contains molecules with the most important one being oxygen. As the air's density changes, so does it's ability to hold a number of these precious oxygen molecules for our engine. Additionally, as the amount of molecules decrease (density decrease) in our volume of air, lift that is being generated from our wing is also decreased. The same goes for our prop's ability to generate thrust, which essentially is just lift turned sideways, lol.

Air density affects your engine's performance, your prop's ability to generate thrust as well as your wing's ability to create lift. "Thick" dense air allows your wing to produce more lift since it is essentially moving more molecules. The same goes for your prop's ability to make more thrust and we all know how oxygen affects engine performance.

Density Altitude's affects on aircraft performance can be very dramatic.

Although another story altogether; when water vapor (humidity) is added to this recipe, engine performance is degraded even more as the vapor in our given volume of air has just displaced even more of our precious oxygen molecules.

I mean no disrespect, but I doubt that you were flying in an actual microburst as these are typically associated with unstable air (cumulous clouds, rain) and are commonly violent (+-75 MPH winds, less than 2.5 miles across). You may have been flying in an area of high thermal activity or huge "bubbles" of air rising from the earth's surface being displaced by the Sun's heat. Remember, if you fly in strong thermal activity, there will definitely be strong downdraft activity as this air has to "replace" itself as it rises into the atmosphere. Oftentimes we under estimate the shear vastness and size of these rising air masses and their associated downdrafts which can literally cover square miles.

Kilowatt

[ZipItyDoDa]

He said the wind was light at the time. He still dosen't know what caused his problem.

There is one incident in the data base where someone had to much pitch in his prop and it was partially stalling until his speed reached 30 MPH or so and it caused him to crash after takeoff because he couldn't gain enough speed to get his prop out of the stall range. Any chance you might have had something like that happening to you?

I actually have my prop pitched less. I peak mine out at 6200rpm. And I have never had this problem with this pitch before. Plus there were others saying they felt weird while flying also. But they were alone, so it wasn't enough to get them into trouble, I guess.

I was up and flying quite a bit. Like I said in the post it wasn't a sudden problem, it just wouldn't go away. I flew 1/4 mile south when I was gaining altitude and then probably about a 1/2 mile north north east, then turned and flew west about a 1/2 mile and then turned south and went at least another 1/4 mile before I landed.

Anyway the post was to alert new flyers that things can look good all the way to take off & climb, and then go bad from there. :rolleyes:
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[ZipItyDoDa]

Density Altitude's affects on aircraft performance can be very dramatic.

Yeah anyone that was at the last ASC flyin at ThreeRivers would know about that. It was a killer that day!!



I mean no disrespect, but I doubt that you were flying in an actual microburst as these are typically associated with unstable air (cumulous clouds, rain) and are commonly violent (+-75 MPH winds, less than 2.5 miles across).

I doubt it too.
I also have had Jeeps that I drive all summer with the hard tops off. I had just gotten done flying my PPC and loaded it up and was just down the road about a mile. All of a sudden I was hit by a wind going sideways to my Jeep. It was so hard and so sudden that I thought my ear drum was going to break! I have driven Jeeps a LOT longer than I have flown PPC's and that is the first time I have ever run into anything like that. I am guessing that's what would have been called a 'micro burst'. Almost like having a semi going past that has a big air wave built-up in front of it. Except that there was no semi, it was at a 90 degree angle to me and it was harder than any semi air wave has hit me.


You may have been flying in an erea of high thermal activity or huge "bubbles" of air rising from the earth's surface being displaced by the Sun's heat. Remember, if you fly in strong thermal activity, there will definitely be strong downdraft activity as this air has to "replace" itself as it rises into the atmosphere. Oftentimes we under estimate the shear vastness and size of these rising air masses and their associated downdrafts which can literally cover square miles.

Kilowatt

I'm thinking along these lines also. But since you can't see these air masses, usually, its hard to say. But whatever the cause it seems to be a very rare occurrence. But still want people aware that it can be out there.
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