djpacro

Newton's Third Law[/url] of action and reaction.

The only way to create lift is by doing that. You may choose a variety of ways to achieve that change in the air flow however Newton is all there is to produce all of the lift.

 

Lift from Flow Turning[/url]I am turning into an engineer so I wouldn't recommend that anyone read the following.

 

... which is where Bernoulli and circulation theory come in.

I'm not sure what you are getting at here Mazda?Bernoulli's theory does not describe a mechanism for generation of lift. i.e. it does not explain any change in velocity however it is useful for calculating the pressure distribution around an aerofoil so used in the advanced Java applet below.

 

Circulation theory? You mean the application of the Kutta condition at the trailing edge? This version of the Foilsim program at

 

FoilSimU Beta Version 1.5a (set it up for Shape/Angle as the Input)

 

enables it to be run with nil circulation therefore no lift is the result.

 

All that tells us is that we need to include circulation theory in the arithmetic otherwise the calculated flow does not represent real life. The real life mechanism is to have an aerofoil with our usual camber and angle of attack to turn the airflow. Panel programs use Bernoulli to calculate and integrate the pressures on the aerofoil. Far easier to do that than calculate the change in momentum of each air particle in the region (although I have seen software which does just that).

 

PS - I must stop this and get back to reading Stick and Rudder - not sure which is harder on the brain at this time of night.

 

and ... I bought Stick and Rudder early last year and found it hard going so only managed to get to page 41 where it sat for many months. This thread prompted me to open it up again and I've made it to page 73. I'm sure that if I had bought it 40 or 50 years ago I would've read right through it in one sitting. My new year resolution is to finish it by the end of January so you're welcome to borrow it then DarkSarcasm.

 

I much prefer the writing style and content of Noel Kruse in Aerodynamics and Other Stuff (apart from the chapter on spins).

 

 

That's pretty much it Qwerty.Bernoulli simply provides a relationship between local velocity and local static pressure.

See How It Flies is excellent, as is Flybetter.com and the NASA website.

Seems like I should expand on this (with a bit of help from NASA).

Lift occurs when a moving flow of gas is turned by a solid object. The flow is turned in one direction, and the lift is generated in the opposite direction, according to Newton's Third Law of action and reaction. Because air is a gas and the molecules are free to move about, any solid surface can deflect a flow. For an aircraft wing, both the upper and lower surfaces contribute to the flow turning.

More at this NASA webpage.Whether it is a flat plate at an angle of attack, or camber, or flapping the wings or rotating the wings or carrying a vacuum cleaner in the cockpit and sucking the air from the upper surface of the wing or spinning a cricket ball - any method of developing lift (thinking off the cuff here but I can't think of anything where it is otherwise) does it per Newton.

A common explanation of how a cambered wing develops lift is via the analogy with a venturi (or half venturi). People seem to easily accept that the velocity increases in the venturi. That is not Bernoulli (yet). More here at this NASA webpage.

 

Knowing that there is an increase (or decrease) in velocity, application of Bernoulli will tell you what the change in pressure is.

 

The static pressure integrated along the entire surface of the airfoil gives the total aerodynamic force on the foil. This force can be broken down into the lift and drag of the airfoil.

For a plain wing, doing the sums with per both Newton and Bernoulli will give the same answer. It is only Newton which explains the development of lift. Bernoulli only shows the distribution of pressure over the wing. (In the case of the vacuum cleaner, Bernoulli won't quite work because energy is being added to the airflow)

 

The air molecules have further to travel over the top of the airfoil than along the bottom. In order to meet up at the trailing edge, the molecules going over the top of the wing must travel faster than the molecules moving under the wing

For an explanation of why that statement is wrong and to see an interesting little Java simulator at this NASA webpage.I can remember a lecturer many years ago explaining that there were male and female air particles. The females went below the wing and the males went the long way so to catch up to their girlfriends they had to travel faster. True! There is no other reason why the particles need to be at the trailing edge at the same time.

 

 

That's pretty much it Qwerty.

 

Bernoulli simply provides a relationship between local velocity and local static pressure.

 

See How It Flies is excellent, as is Flybetter.com and the NASA website.

 

 

Basic Aerobatics Rating

 

Sponsored by Australian Women Pilots' Association

 

One scholarship to be awarded annually to a woman pilot with a minimum of 150 hours total time, to provide assistance towards the cost of a Basic Aerobatics Rating.

 

Value: $1,000 on a 'dollar-for-dollar' basis.

 

Applications MUST be received in writing by 5pm on the 31st of January annually.

 

 

Info on the limited spin testing of the Cirrus is here.

 

The incipient spin and recovery characteristics were examined during more than 60 total spin entries .... The aircraft recovered within one turn in all cases examined ....

 

No spin matrix less than that prescribed in AC23-8A or AC23-15, can determine that all configurations are recoverable. It must be assumed that the SR20 has some unrecoverable characteristics....

 

 

 

 

 

 

 

There's more info on the rationale for the chute as a spin recovery method in that report.Interesting video re-creation of a Cirrus stall accident here.

 

 

It'd be interesting to know whether it is easier for a new student to learn to fly in a Jabiru compared to a Savage Cub, for example.

 

My guess is that time to solo a Cub would be no more than a typical tricycle gear trainer.

 

 

Yes, the 7ECA is certainly under-rated. My friend has one recently refurbished, engine has nearly 2400 hrs TBO.

 

 

I agree, a nice Auster.

 

 

 

I've heard that students on navs have been checked at places such as Hamilton recently.

 

I have an AVID instead of an ASIC, no-one has ever asked to see that either.

 

I operate from Moorabbin, no need for an ASIC there.

 

 

Maj, I agree with you that the American FARs are good - I worked as a pilot and DER there. However CASA has long ago dropped the policy to harmonise with the Americans and now favour the EASA regulations. Unless you are running an airline, I don't like anything I hear about EASA t has had an adverse impact on GA in the UK which was bad enough under the CAA regulations. There is much added bureacracy and onerous requirements in CASA's draft maintenance rules and the associated documentation which will lead to increased costs.

 

This is what the Aviation Maintenance Repair and Overhaul Business Association has to say about the draft regulations in their newsletter of 1/10/09.

 

“CASA recently presented the Attorney General’s drafts of “safety” regulations that are part of the new maintenance package and what it clearly demonstrates is the impracticality of trying to adapt the European regulatory requirements in an Australian regulatory system.

 

Ever since Government/Parliament decided to two-tier the aviation regulatory system and also apply the Criminal Code it is becoming increasingly obvious to all, except those brain-washed by the EASA system, that the outcome will be higher regulatory imposts than is current without any improvements in safety.

 

…

 

The Government conditions are making it hard for CASA to provide outcome based rules. How can you apply the Criminal Code to “outcome-based” law that is suppose to allow participants more flexibility?...

 

Now that these drafts have been seen, it is obvious that aviation needs to return to three tier aviation requirements. Act, regulations and CASA issued ‘aviation safety standards’.

 

The proposed rules will have a negative effect on your long term viability.”

 

PS - the FAA dropped the statement about fostering aviation after the Valuejet accident.

 

 

Michael, interesting post, good to hear about positive experiences like that. I second Matt's comment - warning, aerobatics is addictive.

 

Maz - you don't use Jaguar perfume do you - that might explain something that Michael noticed?:big_grin:

 

 

David, here's an extract from an article that Mal Beard wrote in a local newsletter some years ago.

 

"While Eric Muller recommends the use of in-spin aileron as part of a normal spin recovery,. in some a/c it may have an adverse affect. The use of inspin aileron in a Cessna 150/152 Aerobat has the opposite affect to what you would expect. Inspin aileron causes the spin to go flat.

 

This is the result of the very effective Frieze Ailerons that are fitted to the Cessna wing creating a lot more drag on the aileron that is deflected up.[inside aileron with inspin aileron applied]

 

In the Cessna 150/152 outspin aileron will cause the spin to stop. The reverse airflow through the propeller will cause the motor to stop rotating, just to add a bit of extra excitement and to further raise your heart rate.

 

In the unlikely event that you find yourself spinning inverted in the Cessna it is likely that the use of out-spin aileron will have the normal affect of flattening the spin while in-spin aileron will help during the recovery. This is due to the frieze aileron being in-effective when spinning inverted, as the hinge point of the ailerons is on the top surface of the Cessna wing, a smooth surface is maintained when the wing is inverted regardless of aileron deflection, and A of A should come back into play. Due to a lack of an inverted oil system in the Cessna 150A/152A I have being unable to flight test the above theory inverted, although the use of in-spin aileron to flatten the upright spin has being tested over a number of years and a countless number of spins.

 

A word of warning to anyone contemplating flat spinning the Cessna 150A/152A. A positive hands on spin recovery will be required. Allow several rotations for the recovery to be effective. Also allow for an air restart as the motor will probably have stopped rotating. About 6000 feet plus minimum starting altitude."

 

Extract from an article by Gene Beggs in Sport Aerobatics of October 1985:

 

"In my telephone conversation with Bill Kershner, he told me of a spin mode in his Cessna Aerobat from which he was unable to recover using my power-off, hands-off, opposite-rudder method of emergency spin recovery.... …

 

…...a plain old 1975 Cessna 150 Commuter …

 

If I placed the aircraft in a spin to the left with the power on as might happen with a student who did not correct for the “P” factor properly, and let it spin with the power on for two turns or more, and then cut the power off, released the yoke completely, and then applied full right rudder and held it, the aircraft would continue to spin and showed no sign of recovery evern after as many as 10 turns! I would then place the heel of my hand on the padded center portion of the yoke and briskly push it forward, and the aircraft would always recover promptly in one additional turn ....

 

I found that the Cessna 150 would spin very docile, as long as the ailerons were held neutral and the power completely off in either direction .. Trouble developed only in the spin to the left, either when the power was left on or when “in-spin” aileron was applied and the aircraft permitted to turn two turns or more ..."

 

I haven't let it do as many turns as either Mal or Gene and certainly nowhere near as many as Catherine in that video! 192 ft per rotation ... hmm, a little bit more arithmetic and we could calculate the angle of attack.

 

Cessna produced a booklet in 1978 about spinning and much of that information is provided in this article in Flight Magazine - note that there is no difference in spin characteristics identified between the straight 150s and the Aerobats. Most of this info is also provided in Kershner's book.

 

 

Howdy NYAussie,

 

This Airservices website will show you the local airfields.

 

CASA has a new Visual Flight Guide here (11.2 MB) - 452 pages, a bit of light reading for you.

 

 

Only the "M" model on is legally spinnable.

The Type Certificate Data Sheet for the Cessna 150 lists the following models as being approved for spins: 150, 150A, 150B, 150C, 150 D etc through to the 150M plus the Aerobat variants. It also notes: "Intentional spins with flaps extended prohibited"

 

Djpacro how you would flat spin a C150 is beyond me unless Fat Albert and his mate were stowed away in the luggage compartment (joke). The C150 spins almost vertical, goes through about 2.5 rotations and the airspeed starts to increase (at that point no longer stalled) and you end up rotating in a spiral dive with a face full of ground and a rapidly increasing airspeed.

David, flat spins in a Cessna 150 Aerobat (model M from memory) by personal experience entered from a skidding turn with some power and aileron, also that of two friends, flight instructors (one has his own Aerobat and has done quite an extensive assessment). See this video of a 152 - the spin aggravated by inspin aileron - 60 turns:

Sewanee Aerobatic School - Spin Training

 

I've never had any trouble holding a 150 Aerobat in a multi-turn spin even with power off and neutral aileron. Some examples may have a tendency to spiral, a more positive entry generally fixes it. 152 has a greater tendency to spiral but a suitable entry technique will give a stable spin. Refer also Bill Kershner's book, the Basic Aerobatic Manual - lots of info on spinning the 150 and 152.

 

Djpacro,I hope you had a great day of aeros on Sunday, the Decathlon is a nice AC (don't forget to check the spars). A few years ago I did a 360 degree inverted steep turn in a Decath at Warnervale...had a headache for hours!!! A week later inspection revealed cracks which resulted in the replacement of both wing spars...whoops.

Thanks, was a good day. Another good subject for discussion but, to get back on topic ......I just came across this note in FAA Advisory Circular 61-67C, Stall and Spin Awareness Training: "The pilot of an airplane placarded against intentional spins should assume that the airplane may become uncontrollable in a spin." Next time this subject comes up I will simply refer to that.

 

 

David, you've added quite a few more discussion points there. I won't respond to them all now - off to Lilydale soon for a day of aerobatics and spinning.

 

The type certification requirement for normal category, VLA etc is only to demonstrate recovery from, in effect, an incipient spin - there is no statement regarding recovery from a fully developed spin, especially one aggravated by controls and power.

 

The Grumman Trainer is a well-known example of a type where an unrecoverable spin will develop after a few turns. Nev also mentioned the example of the Airvan earlier.

 

Cessna 172 - if it is approved for spins in the USA then it is approved for spins in Australia - our Type Certificate Data Sheet is a direct copy of the USA one and the original manufacturer's flight manual applies.

 

Cessna 150/152. It can spin flat. Letting go of the controls, or even using the Beggs-Mueller technique (power off, release the stick and full rudder opposite the yaw) will not always result in recovery.

 

Too many friends have died in spins, I am very wary of them although I do some most times I go flying.

 

 

Excellent score, Matt. Time to work on Sportsman for the Victorian Championships.

 

 

Some aircraft enter a spin very quickly in certain configurations. And, having entered a spin I doubt whether the average pilot could recover sufficiently fast ....

Agreed - the entry to a practice spin is often more docile than an unintentional (is it OK to use that word?) spin from a skidding turn. I usually manage to surprise instructor trainees and it is not uncommon to go around a couple of times before he/she initiates recovery action.

 

... I am a law student ...

certainly haven't annoyed me, always happy to debate with lawyers and CASA certification engineers. On the other hand some of my online posts probably unintentionally annoy others - I must put a warning placard in my signature.

2. Is the placard worded wrongly? My Answer: yes, because it leaves the manufacturer open to liability if someone does die in an unintentional spin.

If the manufacturers knew that there was absolutely no way ever that the aircraft could suvive a spin then the placard would probably say NO SPINS EVER ON RISK OF DEATH or something.

The manufacturers don't have a choice on the wording to use in the placard - the regulations are very specific on the text to be used.

 

 

There is a potentially arguable implication that if you do spin it unintentionally then the aircraft will be able to handle it which leaves Jabiru open to potential liability.There is definitely an arguable implication that, if you unintentionally enter a spin, then the aircraft will survive

Yes, up to a point and subject to the pilot doing the right thing as the type should have undergone the limited spin testing required for certification. i.e. not the extensive spin testing required if spins were approved.I used the word "should" as some of these categories are self-certified by the manufacturer. Did they have the controls rigged so that pro-spin controls were at the extreme end of the tolerance and anti-spin controls were at the minimum end of the tolerances etc? At least in the case of the Cessna 162 the FAA took a keen interest (and they were doing the full spin test matrix) so I'm looking forward to spinning it when it is available here (assuming it will be approved for intentional spinning).

 

 

Basically, "No intentional spins" means that, no you can't spin it ok, but if you scr*w up that badly and do spin it, it's not going to fall to pieces

... and you will be able to recover from it if you don't let the spin develop and use the appropriate technique.

Per my earlier post - the regulations are very specific on the wording of placards so the manufacturers don't get a lot of choice. The actual words used would follow from the certification requirements for the particular type.

 

The JAR-VLA requirements borrow a lot from FAR normal category. It has the same limitation of 60 deg bank angle as FAR 23 normal category. It has the same spin test certification requirements as FAR 23 normal category. It is also very specific on the wording of the spin placard but differs from FAR 23 (refer my earlier post):

 

The following placards must be plainly visible to the pilot: ......

 

(b) A placard stating ‘This aeroplane is classified as a very light aeroplane approved for day VFR only, in non-icing conditions. All aerobatic manoeuvres including intentional spinning are prohibited. See Flight Manual for

 

 

 

 

 

 

other limitations’.

It seems that similar offending text is also in the LSA regulations (sorry, I don't have a direct quote).The bottom line is that they should be treated like normal category aircraft i.e. don't spin them.

 

 

I guess I started with a question about grammar and semantics, ie The only reason to differentiate between intentional and unintentional spins rather than just stating "NO SPINS"...MUST be and i repeat my self here it MUST be that unintentional spins are OK.

On grammar and semantics - the FAR 23 requirements are very specific in the words required on placards:

§ 23.1567 Flight maneuver placard.(a) For normal category airplanes, there must be a placard in front of and in clear view of the pilot stating: “No acrobatic maneuvers, including spins, approved.”

(b) For utility category airplanes, there must be— ...........

 

(2) For those airplanes that do not meet the spin requirements for acrobatic category airplanes, an additional placard in clear view of the pilot stating: “Spins Prohibited.”

That text seems to be preferable than the text required by other regs i.e. Jabiru probably didn't have the option to choose the words.

 

As for everything else, as usual, I agree with facthunter.

 

 

Great contest thanks to Grant and his team. Biggest regional contest that I've been to and more serious aerobatic aeroplanes than I've seen anywhere else in Australia.

 

 

Serious practice is well underway at Temora now.

 

More contest aeroplanes than I've ever seen at an Australian contest, even considering the absence of the usual trainers. No Decathlons or Airtourers despite there usually being at least one of each at most contests. Hasn't been a Aerobat at an east coast contest for ages. An Alpha 160 should arrive today.

 

Total Australian fleet (four) of Lasers including one from Perth are here. Two DR-107s. Three different Extras. A flock of single seat and two seat Pitts but a notable absentee is the Camden S-2C.

 

An RV-6, Giles 202, Rebel 300 and an Edge 540.

 

About 30 pilots competing in the five categories.

 

 

thumper & Captain - I have jobs lined up for both of you, the first contest briefing is 8 am Saturday.