Microlighters

Hello Gents,

I need some advice please.

Racking up the Solo hours at Aviators yesterday (pics to follow) I had an interesting experience which i would like to share and get some advice on. I was flying solo in the circuit at AP yesterday and had racked up a great hour an a half of touch and goes, all of which were great, nice landings and great rate of climb on take off. The Bantam does climb well when your alone!! Flying the circuit i would get to circuit height, turn cross wind, down wind, base finals etc and do it all again. On my last circuit I landed really nicely, applied power and headed for the skies BUT, this time i just got NO lift at all, she just did not seem to want to climb!!! I got about 300ft AGL - I thought something may be wrong, but continued flying the plane. All temps and revs were as they should be, no change in anything out of the ordinary, i was just not getting lift... End result I flew a very short circuit, landed it nicely and went back to the clubhouse. Udher, Dale and Piet said that sometimes that happens, you just get caught in a downdraft, keep flying, keep airspeed and you will get out of it.. It was weird for me because i hadnt experienced anything like this before.. it was about 15h00 and it was a hot day... I DO UNDERSTAND density altitude etc, but that wasnt the problem, just a circuit before this one i raced off toward the sky!! Everything was 100 percent, WELL withing weight limits etc...

SO - Im curious - has this happened to anyone.. Had a great chat to thatchman earlier who mentioned some experiences hes had.... anyone else had this type of thing with downdrafts >??

Wind Direction? upwind mountains?

But you could have hit a hot pocket of air with all the symptoms of bad density altitude. It's happened to me, take off Morning Star in my old Chally, heavy, perfect climb, route Altona touch and go, no problem, Wintervogel, touch and long difficult climb, back to Altona, fine and Morning Star.

And you DID remember to hang out the flaps didn't you?. Yes I also had times where in one circuit we'll climb 580 ft/min two up and the next circuit the climb rate resembles something like 120 ft/min. If you have been having say a 15 mph head wind which pretty much died down for a moment as well you will feel the same lack of climb suddenly compared to the previous circuit.

Hey Morph mate - Nothing untoward, wind light, straight down the runway from the north, harties does have the ridge but thats a fair way from the Runway - so no .... nothing weird. As mentioned I had been doing it all afternoon.... just felt like i suddenly had a ton in the plane... anyway all ended very well and i "enjoyed" the experience, i will know for the future....

Cheers chap

Any build up of late afternoon Cb's. FLying towards the cloud you will feel like you are being pushed down, once under the cloud you will be pulled up?

Hi Stephan - yip flaps set, all the goeders in the right places... all good...

Guess these things happen...

Dish

Were you using runway 03 at FAAP? I assume you were, there is some sink just past the numbers (21) above that little stream approaching the highway, don't know why but it is there and sometimes worse than other times, also watch out when on finals for 21 - I have no idea what causes it but chat to Roger or DH and they will confirm the sink right above the end of 03 at FAAP - I once hit it very bad, sold the particular plane soon after - BUT That particular day the wind was doing funny things.

It sounds to me like you are paranoid about lift like someone else I know

D

No not paranoid at all - it was just so strange that it happened ??? wanted to know if it had happened to anyone but thats a great explanation...

thanks

You will probably find that Dale and Piet don't experience this sink in in the Jets they fly

Having said what I have about this sink at FAAP at the end of the runway, I still reckon Aviators Paradise has the best weather ever and that runway is lovely

D

oh yes - without a doubt, this is not a criticism of any runway or airfield at all, each has its own little "features" for want of a better word and each airfield has something to keep an eye out for, so please dont let anyone take this as anything more than me just asking for info and similar experiences. Aeroden for example has the road right next to the threshold of 18. Finals there and one sometimes gets a little Klap while over the road. Rhino has the dam on the end of 27?? if i remember correctly and sometimes you get a little sink over that... so all worth keeping a little eye out for.

In my earlier post I say i will know for the future and thats what its about. its only once you experience something that makes you sit up and think. The power of this forum is such that many lads would have experienced similar and im sure a lot worse in there flying careers, but its only when we discuss that we learn.... Thatch had a huge experience on a return trip from Zebula and related to me what had happened. Sounded scary, but the more aware we are the sharper we become, and in my opinion thats how we learn

How are you big D dad??? getting along nicely with the night rating now ??

Night rating - Eish, ja boet

Keep the throttle open boet.

Harties gets moer hot and there are plenty thermals about (Watch the Cape Griffon Vultures on Sunday) They must have been well inside the TMA ). Never had a problem with the RV, but power to weight it would have to be a moerse downdraft to effect it. Have experienced similar in Cubby at Rand and turning Xwind. Tailwinds tend to do that as does a biggish "warrelwind".... or flying under beeg CB even if it moer high...

Just fly the AOA and the indicated airspeed.

PS
Density altitude is simple. Calc is more complex. I liken it to Scuba diving. Shallow dives hardly any risk. Could almost dive all day. Deeper you go more dangeroos/complex it gets. Similarly with flying it opposite. At sea level all is hunky dory (just like shallow dive). The higher and hotter it gets the harder it for the aerie to perform...


The air density at FAAP is always less than "standard air" and thus the aerie performs (worse). I don't have the manuals with me, but very basically - eg 15 deg C at 1013.2 at the coast is pretty close to "standard". For all increases in temp, alt and pressure the air density (and thus aerie performance) changes. There are formula's to calc DA on Web, but say you flying at FAAP on avg summers day at 35deg C at 4000ft the aerie think and performs as if it at 7122ft... Does not mean much, but convert to % and suddenly the aerie is 43% higher than it thinks it is.... At a given gross weight, increase in density altitude (DA) means a reduction in engine horsepower (thus a reduction in thrust), increased ground speed (thus longer takeoff and landing rolls), and decreased climb performance. The changes can be significant, especially at higher elevations. I would say the 80HP is closer to the 582 numbers.....

It would not have been DA in the above as it would have affected all performance. I would hazzard a guess at downdraft or shift in wind....

Thanks for a most informative post RV.. yeah the more i think about it the more i believe it was just a FAT sink... nothing more

Many thanks all

demon wrote:what time dish my boy? I was flying around hartees at about 5pm yesterday. They wasa big storm to the west causing all sorts of funny stuff, coupled with a 12 knot N wind, was wierd conditions on the hartees side of teh ridge

Saw you buggers checking out westlake. Again looked awesome although the fireworks towards West later on were