do you use a Glide or Power approach??

[Guest pedrok]

Doh

 

first up made a typo now corrected to say "he did not use carby heat"

 

I was taught that Carby ice is more likely because of low engine speed in a glide (page126 of the ATC manual)

 

and

 

To warm the engine on prolonged decents to keep the engine oil warm, avoid plugs fouling and ensure carby heat is on (page126 of the ATC manual)

 

I just rechecked my manual and added the page numbers so its available if wanted (in case Im wrong)

 

But in my response above I was just alluding to the fact the long glides can impact upon engine performance if needed quickly

 

Pete

 

 

[motzartmerv]

Ice can form on the butterfly valve in the throat of the carby, when you close the throttle the butterfly valve closes off and lets a small amount of fuel air mixture through.. This small gap left on the sides is where the ice can cause a blockage. (with this type of iceing that is)..At full throttle or high power setting's the valve is open and thus the gap is large and much less likely to become blocked..

 

cheers

 

 

[Bruce Robbins]

Carby ice forms when the air tempfalls low enough to freeze the water vapour in the air. First you need the water. Dry air - no ice, humid air - potential ice.

 

The temp drop occurs because there is a pressure drop as the air passes through the carby. The pressure drops because the air speeds up going through the restriction in the carby. The smaller the throttle opening the greater the restriction, the faster the air flow, thus the greater temp drop.

 

Carbies are thus more susceptible at low throttle openings. Sometimes the icing occurs while the throttle is low, but doesn't become apparent till you have re-applied power and started climbing away. The ice in the throttle then starts warming up and breaking off.

 

The resultant rough running or misfire sure gets your attention!

 

 

[facthunter]

Cold Carburettors.

 

A lot of the cooling is caused by the latent heat of vapourisation of the fuel. The carb works like a refrigerator. Fuel injected engines still have a throttle body, but they do not ice up as the fuel is injected near the cylinder head.

 

Generally the heat for the carb. is supplied from the muffler/exhaust system. via a "muff". This does not hold much heat as it is only thin sheet metal and cools off when the power is reduced, hence the need to apply FULL carb heat while there is power on and leave it on for long enough to clear all the ice.

 

A little thought about the situation will convince you that longish power-off descents are not a smart idea. The engine is in colder than normal air (due to the altitude), has little heat coming out of it (because the power is off) and has a good flow of air over it due to the high airspeed. The idle is normally richer so the cooled-off plugs soot up. In pre-mix 2- strokes the oil supply is marginal with the closed throttle. Nev..

 

 

[Guest Pioneer200]

As stated earlier, shock cooling of the engine is a concern especially for a longer approach. If you idle it in for the approach, then power away for your circuit you're delivering full power on an essentially cold engine, thus increasing wear and tear. Whilst the actual detriment to the engine may be unmeasurable, it makes perfect sense. Not so bad in a Rotax engine such as the 912 as they are also water cooled, however not brilliant in a Jabiru.

I have always wondered the effects of circuit training has on engines.

 

Full power - cruise power - decent power- idle, repeated and repeated...

 

Can't be good for temps to be rising and decreasing all the time???

 

 

[Ultralights]

we have found circuit work to be quite beneficial with our jabiru engines, in a flying school environment they get worked hard, and funnily enough, flying school Jabirus seam to have the least engine issues!

 

i think the constant and large change in power setting stops the rings getting gummed up with lead deposits, lowers the chances of the barrels glazing over and less plug fouling.. im not an engine man, but it doesnt seam to harm them at all, same goes with out tecnam and its Rotax.

 

our LSA has nearly 6000 hrs on it, and every engine has gone to TBO without any dramas. the only issue was the oil pump wearing out of tolerance.

 

 

[Guest basscheffers]

Power on, every time.

 

The approaches I have been taught are pretty steep, at 65kts. I wonder if I were to respond quick enough with raising the flaps and setting Vbg, how far could I be out and still make the runway? (depends a lot on headwind, of course)

 

 

[motzartmerv]

Why wonder, set yaself up with room to spare and give it a try... Can be practised safely with a nice long runway.. :thumb_up:

 

 

[Guest basscheffers]

Why wonder, set yaself up with room to spare and give it a try... Can be practised safely with a nice long runway.. :thumb_up:

Yeah was thinking about that. Probably not in the busy YPPF circuit. But will definitely give it a go one day.

In the mean time: we have Google Earth and science!

 

I turn final at 600 feet AGL at 5000 feet from the runway. The Sporty is supposed to glide 1:12, so 600 * 12 = 7200 feet, looking good so far, but we have headwind to contend with also. Let's make it 10 knots. That means we'll probably do 45 kts on the ground or so and that is about 4500 fpm. Descending at Vbg is about 500 fpm, so we have 1.2 minutes or 5400 feet to go before we hit the deck. That should also be enough - certainly within the airport fence.

 

So looks like it's entirely possible, just requires very fast reaction and precise flying. But if the engine fails on final or base, raising the flaps before event contemplating thinking about anything else seems like a prudent action to take if you want to make it inside the fence, let alone the runway.

 

 

[Guest basscheffers]

I'll also remember to fly a nice and tight circuit - not alway possible, sharing with the CPL student crowd imagining themselves in a 747 and flying the circuit accordingly, but I do it when I can.

 

One solo session I found myself alone in the circuit and decided to see just how tight I could get them, which was very tight compared to the Grobs and Cessnas usually out there with me!

 

 

[Ultralights]

i did that with the tecnam after a few lessons underestimating its glide capabilities! coming up way to high for a simulated forced landing, so, during a quiet weekend i took it up to 2000 ft, picked a paddock in the distance to see if i could glide it there, and again from 4000 ft, my conclusion, if the field is under the wingtip, you can get there, the jab on the other hand, the usual 2/3rd line up the strut applies.

 

Not long ago, i checked out a very high time Hawaiian Airlines captain in our tecnam, i pointed out the usual circuit at bankstown, and he's response?

 

Why do you fly them so wide? in my 767 we aim for a 1.5 mile circuit!! :ah_oh:

 

so i asked him to show me a proper circuit, and he did! he taught me more in that hour of circuits than i have learnt in my last 500 hrs!

 

fortunatly it was special VFR, 900ft scattered cloud and vis 5000mtrs in constant rain. so we had the entire circuit to ourselves. after take off, climed to 500ft AGL, 180deg turn onto the reciprical heading for downwind, reached circuit height at early downwind, we were no more then 1/2 a mile from the runway, (if you know bankstown at all, we flew the downwind leg pretty much over the airfield boundary near the museum on the south side!!!) we were using runway 11. at mid downwind, he pulled power to idle, slowed the aircraft to about 50 kts, dropped full flap, and conducted a 180 turn/base/final.. and landed exactly on the touchdown zone without touching power once!, we made the turn pretty much about the tower at bankstown! i could only imagine the look on their faces watching these crazy people in an ultralight at bankstown in rain and low cloud doing such incredibly tight circuits turning base and final over the top of the tower!

 

in that hour we managed 12 circuits! i was amazed! during the post flight social chat, i found he had 21,000 hrs total time, in everything from 727's 737's 747 and 767's. in his spare time he flies his P51 Mustang and A36 Bonanza, has hundreds of hours in Tiger moths, Beech Staggerwings, and a SPITFIRE!

 

after just half a circuit, he had mastered the Tecnam, and taught me a thing or 2 about nice close tight circuits!

 

its all about ENERGY management, full flap and 50 kts in a tecnam =1000 to 1500ft/min ROD, and rule of thumb is as you pass over the fence, speed should be 1.3x stall speed. if the aircraft stalls at 45 kts, then approach speed should be 58kts. instead of using power to maintain speed and overcome drag, use the rate of descent...the aircraft flying energy comes from gravity, not engine power. this is how we managed such tight steep circuits and kept approach speed at 55 kts to a perfect landing with no float whatsoever. timing the flare is everything.. for obvious reasons.

 

i would highly recommend practicing such slow speed flight and descents with an instructor, and start at a decent altitude and practice at height before attempting such maneuvers close to the ground.

 

apparently according to the Boeing ops manuals, a 737 circuit should be 1 mile, a 767 is 1.5 miles and a 747 only requires a 2 mile wide circuit.

 

I am an advocate of such landing techniques, as i have had an engine failure on mid finals. over a built up area. fortunatly i was doing a glide type approach, and made the strip easily. thought the pucker factor was high as you fly an approach with a stopped prop in front of you.

 

and the failure was mechanical, not related to icing or other caused by long power off descents. :)

 

 

[Guest Pop-top]

I'm learning both but I love it when I get to side slip! :thumb_up:

 

ie practice forced landings and engine failures are my glide approach practice (or sometimes when there is hardly any wind)

 

Most landings tend to be powered approach - only because I like to think of what it feels like as a passenger on a boeing and when you can feel the pilot apply power and adjust it etc :big_grin: makes me feel like I'm living the dream and not a student in an ultralight ;)

 

 

[Guest basscheffers]

Why do you fly them so wide? in my 767 we aim for a 1.5 mile circuit!!

At which point is this measured?

I was told by a friend that his brother, a 767 pilot also, at the end of a sim session did a "tightest Heathrow circuit competition". I think someone managed to do it threshold to threshold in under 2 minutes! Probably a particularly lightly loaded 767, but pretty impressive none the less!

 

 

[Modest Pilot]

For air-cooled engines a power approach is probably a good idea if you are looking at reaching the recommended TBO. However there's always the chance of an engine failure to consider. During testing the Aerocarb on the Sonex jammed on approach at 600 feet just as an area of high sink rate was encountered. This is a known problem on slide type carbs, the fix being to stop the engine reset the throttle and restart. Seemed a bit sporty at this altitude, so I went from landing to T/O flap setting and comfortably landed. The Sonex flaps have very high drag in landing config. But my J230D will do the same but only just.

 

If you are thinking of doing this even though it's an emergency situation you better have a minimum altitude for config changes, I use 500 feet on the J230. (I use 70kn approach speed primarily for better aileron control so you have 10kn speed to play around with) On the Sonex I use the flare point and before people start jumping up and down, remember the B747 Go Round calls for Go Round Thrust and flaps to T/O position and that can be from under 20 feet! The point being that much depends on the aircraft.

 

 

[Ultralights]

At which point is this measured?

im not exactly sure, i would assume its from the runway centreline.

 

ill find out exactly when i get a chance.

 

 

[Yenn]

I wonder how many of those accidents where the plane landed short, were due to engine stoppage during a power on approach.

 

 

[Guest 3rd dimension]

Just a quick note.

 

I think everyone should read the book "Stick and rudder".

 

I am not saying that his ideas are the final word - but he makes a lot of sense.

 

I was trained in GA, and was taught to use a little power on finals.

 

In a Cess182 and piper arrow you need it to grease it on.

 

Stay safe and fly nice - Adam

 

 

[Ben Longden]

Doing the math, a three degree approach requires a 350ft/min descent at the published fgure of 60kts in a Tecnam. Depending on wind (from outside the cockpit) numerous throttle, stick and rudder adjustments will need to be made to maintain approach for a greaser.

 

So... its a combination, I guess...

 

Ben

 

 

[facthunter]

Approach slope.

 

The standard glideslope is about 3 degrees which is generally considered a bit flat for the more draggy. (poor L/D) ultralights. That angle gives you about 3,000' (AGL) at 10 miles. Your sink rate depends on GROUNDspeed, always, if the approach angle is constant, and you would be about one and a half miles out at your 500' final position.(That's probably a bit more than you need). Nev.

 

 

[poteroo]

Best advice is to learn how to do every type of approach : +/- power, +/- flap, slipped in all configurations, squared circuit v racetrack, and so on - so that you'll be able to use the most appropriate for the situation on the day. Who knows - it might be your BFR day!

 

happy days,

 

 

[farri]

The ideal situation is where the runway can be safely reached in the event of an engine failure, with each and every final approach,either with or without power applied and both methods should be perfected as there is place for each to be used.

 

Example.

 

While doing a glide approach,a heavy sink is encountered which will cause the AC to fall short of the runway,power must be applied to arrest the sink and maintain or regain height.

 

I have no problem doing approaches with or without power, however,with turbulent and windy conditions I may choose to power on to the ground because this gives me more control of the aircraft and I can pin it to the ground better.

 

Choose the method the best suites the situation.

 

Cheers,

 

Frank.

 

 

[JG3]

Glide approach for sure!!! Just because it's a heck of a lot more fun!!! Power approaches are about as boring as driving a Kingswood automatic - just steer and more or less throttle. I consider flying by power to be 'driving' an aircraft. The real 'flying' starts when you pull the power and start gliding......

 

A glide approach requires simultaneously sensing and calculating so many factors that make it an interesting challenge. Balancing aerodynamics, height, speed, momentum, lift, drag, wind, gravity, etc to effect a gide slope that will set you down just where you want. And I do mean always aiming for an exact touchdown point, just as if it's a spot landing competition. Power off at the start of base, and the rest of the way by balancing all those factors. It's really satisfying to get it just right. Takes lots of practice, but that's the fun! Up and around in a short circuit just so I can do another glide approach, over and over again. Deliberately set up high and try to slip right down to the point. Set up low and practice very best glide. Particularly fun if there's lots of wind to figure in, and extra good with a x-wind. Every approach is a bit different so a new challenge. That's why it's so much fun - can do it for hours.... And you can sure get good at it with lots of practice, so it's really satisfying. The closest comparison I can make that's so much fun is down-hill skiing - ride up to the top just to be able to do it again and again.

 

At my home airfield of Kilcoy, Qld there will sometimes be 3-4 of us all following around for multiple glide approaches - maybe a dozen or more in quick succession - a heck of a lot of fun!!!

 

p.s.- Also satisfying to know that you can dependably do it into a paddock if the engine really does quit, no way you're really ready for that without frequent practice.....

 

JohnG

 

 

[bushpilot]

Mostly power on for me; all the time on my farm strip - which is uphill and I often land with tail-wind. Power on helps me match the uphill slope in the roundout / flare and is kinder on the undercarriage (J160).

 

 

[eastmeg2]

The standard glideslope is about 3 degrees which is generally considered a bit flat for the more draggy. (poor L/D) ultralights.

3 degrees is a 19:1 glide slope. Can your average GA aircraft actually achieve this without power or is it a slightly powered approach?

 

 

[Barefootpilot]

No is the simple answer to the 3' degree question. Single engine aircraft doing a 3' approach are setting themselves up for an out landing! The minimum should be at least a 5' profile and even this is at the limits for most GA aircraft. (of course that all depends on wind!)