lee-wave

On 04/04/2021 at 8:44 AM, Peter Piper said:

I'm late to this soiree , but that might actually allow me to assist you better. Allow me to state my credentials, fellow aviators: I graduated in the top 1% of highschool students, and studied a little physics at university and a little maths as a post graduate. I carefully read the thread that the administrator closed. It seems to me that it is important to Mr Emu to discuss this but, like most of us, he is distressed by not being listened to when he has gone to so much trouble. Mr Pen was rude and stated his case without listening to Mr Emu. I might also add that I was a member of the Philosophy Club at university and like precise language.

 

 

Beat you there... I graduated top 100% of primary school students in Fiji and studied a little bit of basket weaving...

You come across two identical objects in deep space.  One is filled with duck feathers the other is full of Osmium (twice the weight of lead).  How would you determine which one was the feather filled object and vice versa without touching it ?  in other words which object had the greater mass ?

The latest government guidelines to the resumption of GA.   With luck should be back in the air by early April....

https://www.gov.uk/government/publications/coronavirus-covid-19-general-aviation/coronavirus-covid-19-general-aviation

7 minutes ago, planedriver said:

So do you know what happened to "Little Nellie" out of curiosity?

It's probably worth a lot more than it's build cost these days, if it's still around somewhere.

Your thinking of Ken Wallis of autogyro fame ..... Barnes Wallis was the Wellington bomber (geodetic), bouncing bomb (dambusters), tallboy bomb (Tirpitz) designer.  

On 14/02/2021 at 10:12 PM, old man emu said:

Lee-wave,

This is a family-friendly forum. Please avoid using obscenities when describing foodstuffs.

Nice one 😁....it happens to be the village where Barnes Wallis hung out.  He is buried nearby...

On 04/02/2021 at 11:07 AM, planedriver said:

You are probably at Redhill. I know it well.

Just keep the Jabby away from my nephew who flys his models not far away. 

Not at Redhill. Parked on a private strip near Effingham.  There is a Jab powered Easyraider in the background. 

About 4- 5 inches of snow fell last weekend in Surrey.   The following day I went for a walk to check out the Jab.   Poor old thing has not flown since Sept 2020.  With the thingy going on we all wonder when will we get airborne again.... no one seems to know.  

On 10/01/2021 at 2:40 AM, Yenn said:

Two things stand out from this discussion. We seem to be unaware that no single control works the way it seems. By that I mean that the ailerons do not cause a turn and the application of power does not cause a climb. There has to be some other control input at the same time, except maybe when we have no power.

The other thing is that the "downwind turn" or whatever you like to call it is still alive and well. When we fly, we are flying in a parcel of air that is probably moving. All our inputs affect the planes location in that parcel of air. One of the big problems which causes the stall spin in base turn is that we are no longer flying in that parcel of air, but are using the stationary ground as a reference. That is stuffing up our interpretation of what the plane is doing.

If you low fly you have to fly the plane in the parcel of air, plus you have to be aware of how that parcel of air is travelling across the ground. Not having that knowledge and being able to use it is what causes the problems.

As far as I can read Yenns is the only reply that addresses omes original question.  The most dangerous part of a circuit is the turn from base to final where the pilot has to contend with a visual illusion..... 

If the wind is of any strength straight down the runway then visually, despite the pilot making an accurate coordinated turn, he would think that the aircraft is skidding and subconsciously apply more rudder.  If you add to the equation the lower airspeed and the reluctance of many pilots to bank steeply near the ground then the result is a perfect set up for an entry into a spin....

I remember, quite clearly, after glider tow #21 in a Cub or Pawnee, tired and probably dehydrated, shouting out to myself 'feet off the rudder pedals'...  better a slipping turn then skid... that is also how I taught hundreds of glider pilots...

I purchased SkyEcho primarily because of the 50% rebate that the CAA is offering.   All I need is to see and be seen by other aircraft that are nearby. Don't really care about aircraft more then 5 miles away or flying in controlled airspace above .  When connected to Skydemon other aircraft show as lines depicting their heading. If they present no conflict then, again, why should anyone be interested in seeing them.  More aircraft on the screen would only clutter up the display.  

13 hours ago, Tex said:

Agreed erroneous. L/D is not just best glide. Best L/D also changes i.e with weight, as does your glide ratio depending on many factors and more than just published polar data (lets avoid McCready theory discussions).

 

Required glide ratio or a required glide slope: Same thing, if you have it = safer. Again what relevance is ILS terminology to VFR rec aircraft? None. When I fly a glider my instruments tell me when I am above the required final glide slope and even give the cross section required GR, actual GR (avg) If you have a glide approach you are above or on the (required) glide slope. Pretty simple.

Lift drag ratio or L/D is the same as glide ratio......varying weights do not affect the LD of the aircraft or glider; only the speed at which best LD is achieved. On good thermal or ridge soaring days gliders are loaded with water ballast. The extra weight had the effect of raising the best L/D speed allowing for much faster inter thermal speeds. The price was a slightly slower climb performance.  If conditions weakened the water could be dumped.              

.......and should we 'learn to glide' powered aircraft ... absolutely we should with the motor switched off (the Jab motor does not take kindly prolonged idle glide approaches) and preferably with the  prop not rotating into a nice long grass or sealed runway into wind.   The Jab UL has a very good glide ratio of 13:1 at around 60 knots.  Also practice side slipping as much as you can even during normal approaches.  

Merry Christmas everyone from a completely lock downed, miserably wet UK....

On 01/12/2020 at 9:06 PM, old man emu said:

I should have simplified the whole bloody thing by not posing the question at all. I pose a serious question and get stupid responses. There are times and places for wit and repartee. One of these is called socialaustralia.com.au. 

 

The point of the question, and, dare I say, the title and location where it exists, indicate that it is something to be contemplated in light of pilots' supposed knowledge of the properties of the atmosphere and the effects those properties have on Man and machine.

There was no intention to ridicule your question....but the heading of your posting was 'an Air density puzzle' and then the question you posed was 'which ship would travel faster in the two different regions assuming both identical ships were sailing (in a steady state motion) directly downwind in a steady 10knot wind'.   

Most people would assume that your question is.. 'will different air densities affect the velocity of the ships ?'.  The answer is a lot more complex then you might think...

Before you can answer the question the velocity of the wind has to be calculated in the same way pilots calculate TAS and CAS. 

Generally TAS and CAS are within a few knots of each other in an aircraft but for ships in different regions of the world not only would the atmospheric pressure be taken into account and measured very accurately but the atmospheric temperature will also have to be measured very accurately to make sure the wind velocities are identical in both regions of the world.  There was some suggestion of using a hot wire anemometer to measure the true wind velocity which is good thinking along the correct lines...

Assuming some very clever person has got the wind velocity absolutely spot on and assuming the density, temperature and salinity of the sea in both regions are identical......... repeat the question.... which ship will travel faster?    and the answer is..... the ship sailing in Alaska will 'go faster' by a very, very small margin.    why ?  

17 hours ago, old man emu said:

Here's a little puzzle to divert you attention for a while.

 

There are two identical sailing ships. Their masses and rigging are exactly the same. 

One of the two is sailing from the Alaskan island of Kodiak (58 degrees North), while the other is sailing from Mackay, Queensland (21 degrees South)

 

If both ships have a direct tailwind of 10 knots, which ship will be expected to go faster? (disregard the effects of water density)

You could simplify the whole question...take two identical kites each in the locations mentioned. Tie the strings to a calibrated spring balance.  Which one would be pulling harder in a steady ten knot breeze ?

In almost 2k hours gliding I have intentionally entered cloud on only a half dozen occasions pre GPS using Turn and Slip and the airspeed indicator as the primary means of staying in control.  

The trick was to transition onto those instruments at least 200ft below the cloud base noting the compass heading for the direction you wished to leave the thermal and not moving your head.  Once in the cloud the turn was continued keeping the turn rate as constant as possible again without moving the head.  When straightening out to leave the cloud the sensation that you were turning the other way was quite strong. I would tilt my head to counter this sensation and stay concentrated on the Turn and Slip until clear of the cloud.  In a retractable glider I would also lower the undercarriage before entering the cloud.  The extra drag helped to stabilise the speed and the added sound would aid airspeed control, but in any case if the airspeed started to increase rapidly airbrake was immediately deployed.

Found out quickly that the time spent in the cloud wiped out the extra altitude gained and those gliders that stayed below the cloud were always much faster round the course.

The real point to be made here is that you cannot just flick over from visual to IMC in an instant. It takes time for the brain to adjust to the transition.  The fanciest piece of electronic equipment would not have prevented the upset and near fatal incident.

Certainly a shocking video to view, but more disturbing is the total inaction of the person in the rear cockpit. Was he a qualified instructor? was this a bona fida training flight or just a jolly with the owner of the aircraft in the back seat.

Up until the camera dislodges, you can see that the front seat driver never uses the rudder pedals...his feet never move  The yaw string fixed point is like an arrow head pointing to the rudder that needs to be pressed.  So he is either not a glider pilot or someone who has never been shown what adverse yaw is.  In either case I am amazed that the person in the back seat (presumably P1) did not take immediate control of the situation and fly the aircraft out of trouble....

RFguy .. a good question.... my son is currently exploring that area of low speed flight in the 170.  Having flown for a couple of hours recently in the real thing I think he is in a good position to tell the difference.  We think the control input and effect in the sim is very real but the aircraft seems to lose energy far quicker then the real thing below 55 knots....more to come...

Jerry the visuals are out of this world...Jackrells is where I fly down to for the annual permit. The inspector has a 270m one way strip that you can just about see to the left of the Jackrell farm label...but we both agree his strip is a bit too short for the Jab.

Managed to hook up Skydemon to FS2020... now there is the capability to practice navigation with SD and also brushing up on flight planning using the paper charts with the E6B all in the comfort of your living room.   It is important to maintain the old skills of flight planning in the event the GPS signals are lost.  

Some pictures of the Jab in FS2020. The 170 is very realistic...all controls work via mouse or on assigned buttons.  Currently I am practicing flying in the right seat ie left hand on stick right hand on throttle.

Also arrived yesterday is the Skyecho 2 ADSB in/out. Only legal to carry in the UK and Oz.  The aircraft hex number is added during set up so ATC  can see and Id without a squawk. When wirelessly connected to SD all ADSB out and Flarm aircraft nearby show up on the screen.   CAA are offering a 50% rebate on purchases so it is a bargain. Also can bluetooth connect to headset for an audible warning such as aircraft in potential conflict.   

On 12/11/2020 at 1:04 AM, facthunter said:

It's commonly agreed the most rapid wear is after start up but I don't think that equates with pulling it through by hand. I'd do that say once a month and spray a storage oil in each cylinder with it's piston at bottom dead centre. The WORST thing to do is leave your plane near the clubhouse, then later in the day taxi it a few hundred meters to the hangar  and not use it for a few months.. Nev

I still believe that what happens during the shutdown phase of any motor will have a direct effect on the wear and tear on the next startup.  Added to this is the method by which the Rotax and Jab motors are shutdown compared to, say, a Lycoming.  By starving the motor of fuel in a Lycoming using 'ICO' there is less chance of detonation and less/no fuel present to wash away the oil in the cylinders walls.  Turning the fuel cock off and letting the motor stop of fuel starvation in a Jab or Rotax is almost identical to using idle cut off in a Lycoming or Continental.  

lw

For sure I let it cool down before rotating prop.  There are schools of thought re leaving a dry carb bowl for long periods of disuse. Do the 'o rings /seals dry out and become brittle etc... but from the UK Jab motor guru (my brother) for the past 25 years of Jab motor repairs he has not seen any problems with wet or dry carb bowls.

As an aside I use Esso 97 synergy mogas during the summer.  It is the only fuel guaranteed not to have any methanol additives.  

Toward winter, like now, I start filling with Avgas, so that there is mostly Avgas during Dec/Jan in the wing tanks. 

So far I have not done a full inhibit on the Jab because, on my mainly chalk strip on the north downs,  the drainage is very good and there is always the opportunity to fly at least once a fortnight....

Probably discussed before but what are your thoughts re flring up the motor for ground runs every now and then...? 

My flying is fairly infrequent so I am trying this procedure on the hydraulic lifter Jab motor.   

At the end of the flight fuel cock off,    allow the motor to run out of fuel and shut down.   All electrics off.  Rotate the prop through a couple of times.  The thoughts there are oil has not drained or been washed away by the fuel, is less viscous so will readily coat all surfaces.

Before the next flight rotate prop as normal. It is important for me to feel good compressions on all 4 cylinders.

Then I press the starter for 5 seconds without the ignition on.  Then fuel cock open, 10 seconds on the fuel pump to refill the carb. 

After that choke fully out, throttle completely closed (engine will be harder to start if idle is set too high). Engine always starts instantly.  Do not touch the choke or throttle for at least 20 seconds.  Thereafter everything as normal.

Any comments on these procedures...?

I would be interested in learning from other users the finer points of the simulator that you might learn from trial and error.... here's one.. only on airfields as marked can you begin a flight. If you choose your unmarked home strip and press go fly you will be at 6.5k ft. and will have to descend and land before you can begin circuits for example.   if you crash and restart you are back at 6.5k ft.  Not a big deal but if anyone can find a work around for this and I am sure other things that are going to crop up please share.

I plug via the Graphics card HDMI on the PC into a 50'" Samsung smart TV.  Recommendations by the store was to run at 1080P at most but when set up the resolution default was 4K 2K which I left it at and it seems that the graphics card can handle the rendering when flying normally.. however when flying the Pitts (120hrs in my real log book) and doing snap rolls for ex., there is pixelation and a lag in, say the clouds or the hills.  I raised the frame refresh rate from 30 to 60 which makes for smoother and very realistic scenery but at the price of a CPU running very hard and the extra cooling fans coming on....

anyway more to come....as I learn...

As my main Dell Inspiron PC was 13 years old, I decided, before lockdown II, to bite the bullet; get a high end gaming PC from a store that built up the PC specifically to run the FS2020 software.  Figured that if things did not run smoothly then the store would fix it.  Also purchased the Jabiru 160/170 add on.  If anyone is interested the best platform to receive your games is Steam.. check it out.. you can purchase and download virtually any gaming software.  Total cost in UK money was £1,700

My download broadband fibre speed is typically 35mbits/s.  Total time for download was 8.5 hour including several complete 'stops' when the software download freezed even though the internet connection remained at max speed....on those freeze occasions there was no alternative but to restart the download which, thankfully, started from where you left off. So if you start the download before bedtime you might be disappointed in the morning.

Once the software packages are downloaded and the game is up and running you quickly forget the glitches. I was blown away by the graphics and scenery.  The software is constantly evolving and updating and I believe more and more features and airfields will be added on.  

Just to add that I can now practice flying in the right seat of Jab ie stick left hand and throttle between the legs.

Would love to hear of other peoples experiences of FS2020....looks like like this is all the flying I am going to get for the next 2 or 3 month. 

First sentence absolutely agree, second sentence I do not fully understand...but I would like to know how a static thrust on a fixed pitch propellor is carried out without the special equipment as was used in the article. 

While researching performance and static thrust on my 60x42 Jab propellor I came across this fascinating article.  The Jab propellor under test happens to be the exact same type as fitted to the factory built UL-D.

It is hard to believe that a small wooden prop rotating at around 3000 rpm can push (or pull) the aircraft along with a thrust of approximately 130 kg.

Static Thrust.pdf

Other than being unsightly and smelly (an odour I dont mind) does the risk of cow pats coating your empennage worry you??

When the weather is good for flying I communicate with the farmer...the day before flying the cows are moved off the strip. There is an electric fence post which runs a wire down the length of the strip and toward the windsock on the left. In the morning I roll the strip. You can see the rolled section of the strip. This flattens the cow pats and very little is flung up onto the aircraft. I try not to taxi over long grass which does no good to the prop tips...in fact does anyone have a spare 60" x 42" Jab prop floating around?

Thanks Alan....

For the price / performance ratio of the Jabiru I believe there is no finer microlight aircraft available....being of composite construction it can live outdoors all the year round with covers....it can cruise at 90 knts burning just on 15ltr/hr. The take off and landing performance is outstanding for a true 80 hp motor. The only other similar aircraft of composite construction and performance is the Pipistrel Virus which costs 3-4 times as much even for a second hand example. In these strange times the Jabiru keeps me sane and socially distanced from my fellow human beings......

In the UK the annual permit to fly check flight needs to be carried out at near to mauw as possible.

My strip being marginal at 290 mtrs I first found a 'victim' who weighed around 70kg to be the ballast and then did a solo takeoff at 450 - 70kg = 380kg. I then calculated the extra takeoff length at 450kg using a 10kg/10mtr ratio and then carried out the second fully loaded 'check flight'.

The 2 flights were only a half hour apart as you can see from the suns position so ambient conditions were near to identical with about 5 knots of right hand x wind, 23C and 1013 HPa. Lift off for both flights was 53 knots and the speed allowed to increase to 68 knots for the climb out. Flaps were at the first detent. I estimated 2-3 litres fuel burned for the 380 kg flight so the second flight was around 447kg.

Unfortunately a cow just about blocked the exact lift off point for the 447kg takeoff but you can see how much flatter the heavier take off was using the tree as a reference point (the sun was also lower in the sky). After the test flight I paced the extra takeoff length and it was roughly 90 mtrs ± 5mtrs....a lot further then calculated....something I thought about later over a beer.