A thread in AVSIM that took a strange direction

[taildraggin68]

In regards to taxiing, I had more time in a plane than a car when I turned 16, in fact having no experience at all in a car until just before my 16th birthday in "Driver's Ed". So I guess I'm one of the unusual ones and the car was actually more difficult for me to transition to.

As far as the original post, yes it is unusual in my "opinion" to form an opinion without the benefit of knowledge or experience on the issue the opinion is about. In fact if all of the "flight sim" models were to the level of A2A in accuracy, then quite a few developers wouldn't make any money as the workload required of that fancy Airbus 318 in conjunction with actual physics accuracy would daunt most casual simmers.

In fact I now expect to hear a stall horn and feel the mush if I rotate too soon and sharply. I expect to be able to slip if I need to. I expect something to fail if I didn't do my preflight.

Most sim addons anymore are trade offs in realism for eye candy and systems (not going to be able to actually slam the throttles on a certain Pilatus Turboprop and get to 2000AGL without soon looking for a place to put her down).

Some people just want an easy button....

[Nick - A2A]

After that post (last night) I tried a little slow flight in the A2A 172 - and I can generally keep the horn blaring between the bottom of the white arc and below 40kias (one person, full fuel, full flaps, S prop).

That's interesting Rob, I definitely can't seem to get her below 40 kias (not that I particularly want to!) even with less weight on board and wheel fairings, flap seals an so on installed. To tell the truth, I find it amazing that a real C172 would be controllable below 40 kias which is why I was curious about the differing white arcs on the ASI's installed on real-world examples.

When I try and reach the slow end of the flight envelope, I can hold the aeroplane at 40 kias in quite a rapid sink but I run out of pitch authority if I try and go any slower - or drop a wing. (Of course - this may just mean I haven't got 'the right stuff'! )

However, this does seem to match exactly the behaviour I'd expect if that white arc did stop at 40 kias. As I can't imagine many pilots of C172's attempt to fly around at speeds between 33 and 40 kias, I'm guessing it's something of a 'grey area' in the real thing?

Thanks,
Nick

[Great Ozzie]

As I can't imagine many pilots of C172's attempt to fly around at speeds between 33 and 40 kias, I'm guessing it's something of a 'grey area' in the real thing?

When I did my PPL etc, it was called "slow flight at minimum controllable airspeed". You worked at hanging off the prop with the stall warning horn squealing. The instructor wanted that horn to stay on during the four fundamentals (in this case, gentle turns, climbs, descents, straight & level). It is one of those maneuvers that gives you a good idea of how the airplane handles down in that airspeed regime... the same one you get into when you are going into a landing. (edit: or as taildraggin pointed out above, can get into on the departure)

It's like anything... time and practice and getting set up for it.

We didn't stay a long time in that configuration in the summertime, as there is not a lot of cooling going on. Still have to demonstrate "slow flight" (it's in the PTS) but I am not sure what kind of speed would be picked by an examiner these days. I certainly would want to make that the goal (being in the horn sounding region) whether or not it is going to be on the practical.

"Anytime".

[Oracle427]

As far as my training went you definitely need to perform the 4 fundamentals with the stall horn on the entire time while holding altitude. In an S model that would be around 40Kias. It's a lot of fun to practice and transition to and from slow flight.

I am unable to get the break below the white arc. It's really close but no matter how steady I try to hold it, the nose drops before then. The break is very close at around 2 to 3 knots. Honestly I'm not sure what happens in the real deal because I'm definitely not watching the airspeed in slow flight.

[computerflyer]

In regards to taxiing, I had more time in a plane than a car when I turned 16, in fact having no experience at all in a car until just before my 16th birthday in "Driver's Ed". So I guess I'm one of the unusual ones and the car was actually more difficult for me to transition to.

As far as the original post, yes it is unusual in my "opinion" to form an opinion without the benefit of knowledge or experience on the issue the opinion is about. In fact if all of the "flight sim" models were to the level of A2A in accuracy, then quite a few developers wouldn't make any money as the workload required of that fancy Airbus 318 in conjunction with actual physics accuracy would daunt most casual simmers.

In fact I now expect to hear a stall horn and feel the mush if I rotate too soon and sharply. I expect to be able to slip if I need to. I expect something to fail if I didn't do my preflight.

Most sim addons anymore are trade offs in realism for eye candy and systems (not going to be able to actually slam the throttles on a certain Pilatus Turboprop and get to 2000AGL without soon looking for a place to put her down).

Some people just want an easy button....

We usually hear about students trying to steer an airplane on the ground using the yoke due to their automotive reflexes. Learning to fly first and then transitioning to a car is very unusual. It must be "interesting" when such a student in Drivers' Ed. tries to steer the car using the clutch and brake pedals.

[taildraggin68]

In regards to taxiing, I had more time in a plane than a car when I turned 16, in fact having no experience at all in a car until just before my 16th birthday in "Driver's Ed". So I guess I'm one of the unusual ones and the car was actually more difficult for me to transition to.

As far as the original post, yes it is unusual in my "opinion" to form an opinion without the benefit of knowledge or experience on the issue the opinion is about. In fact if all of the "flight sim" models were to the level of A2A in accuracy, then quite a few developers wouldn't make any money as the workload required of that fancy Airbus 318 in conjunction with actual physics accuracy would daunt most casual simmers.

In fact I now expect to hear a stall horn and feel the mush if I rotate too soon and sharply. I expect to be able to slip if I need to. I expect something to fail if I didn't do my preflight.

Most sim addons anymore are trade offs in realism for eye candy and systems (not going to be able to actually slam the throttles on a certain Pilatus Turboprop and get to 2000AGL without soon looking for a place to put her down).

Some people just want an easy button....

We usually hear about students trying to steer an airplane on the ground using the yoke due to their automotive reflexes. Learning to fly first and then transitioning to a car is very unusual. It must be "interesting" when such a student in Drivers' Ed. tries to steer the car using the clutch and brake pedals.

We won't even say how bad the clutch/gas pedal fiasco was other than my Dad put me in the driver's seat of a Standard in Downtown Atlanta and just said drive......no instruction other than just do it We as well as the surrounding populace survived with me figuring out the clutch and gas real quick

[Nick - A2A]

Thanks guys - some interesting posts. I'm still unable to achieve sustained, controllable flight anywhere below 40 kias in the C172, even with just a pilot and minimal fuel on board. Conversely - in my beloved Cherokee - I can tool away to my heart's content at the bottom of the white arc. However, the bottom of the white arc on the Cherokee is about 48 kias (55mph) vs. 33 kias in the C172!

As I say, not a criticism of the flight model as such. I'm just curious as to why the bottom of the white arc is 33 kias in some C172R's and 40 kias in others...

We won't even say how bad the clutch/gas pedal fiasco was

Taildraggin' - so long as you didn't pull back real hard on the steering wheel in a vain attempt to clear the heads of innocent pedestrians... All's good!

All the best,
Nick

[Scott - A2A]

Nick,

We've just recently modeled airspeed indicator errors, which will make it into a future update for the 172. This brings the stall speeds down.

Scott.

[n421nj]

Find a nice headwind.

[Nick - A2A]

We've just recently modeled airspeed indicator errors, which will make it into a future update for the 172. This brings the stall speeds down.

Sounds intriguing! Thanks for the info Scott.

...Edited a bit later to add the following:

Have done a little more reading on the subject of the varying white arcs on C172 ASI's. The links below contain a bit more discussion on the subject which I've found instructive:-

http://www.pprune.org/tech-log/59735-ce ... speed.html
http://www.cessna172club.com/forum/ubbt ... ber=144183

The video below does a good job of illustrating Great Oz's point about "slow flight at minimum controllable airspeed". It also shows that the bottom of the white arc on the ASI doesn't necessarily coincide with the landing config. stall speed.
[youtube]http://www.youtube.com/watch?v=yPG05Dz8P6c[/youtube]

Anyway, this is what I can't seem to manage in the Cessna - controlled level flight at speeds below 40kias. Will experiment a bit more as time allows...

Cheers,
Nick

P.S. Apologies to Oracle for the slightly OT post/thread drift.

[Scott - A2A]

Nick,

You will be able to do controlled flight at lower indicated speeds when we release the new code, simulating the airspeed indicator errors.

Scott.

[Oracle427]

That makes sense to me. In the back of my mind I was thinking that the simulator might not be accounting for instrument error at the high AOA as the margin between CAS and IAS begin to spread at the very bottom of the white arc. Cool to know that this is being modeled!

Oh Nick, I'm one of most prolific topic hijackers. No need to apologize.

[Nick - A2A]

Thanks for the clarification on the forthcoming ASI update Scott. Looking forward to it... Was just curious as Great Ozzie and Oracle seemed to be reporting rather better control down to the bottom of the white arc than I've been able to achieve with the current build; this led me to wonder if something was amiss with my setup other than just 'finger trouble'. (Hence experimenting with the speed mods etc.)

By the way - I've been looking at a few more photos of C172R cockpits, and I've got cause to revise an earlier statement I made...

I've looked at a few photographs of real C172Rs and noticed that for the majority of examples, the ASI white arc starts at 40 kias. The white arc in the A2A C172 starts at a significantly slower airspeed - 33 kias according to the POH. However, other real examples of C172's do also feature this ASI.

...I'd only looked at the first page of results on Airliner.net. In truth, the majority of R models like this one are fitted with the ASI with a white arc which goes down to 33kias. However, there are also some C172R's with the white arc which stops at 40kias. From what I can see of these – and here's an example – the tachometer green arc extends to 2,700rpm so I'm guessing they're 'S' equivalents fitted with the 76" 60° prop or similar? (so they get fitted with the C172S ASI too)

Thanks,
Nick

[Oracle427]

No clue on the ASI differences.

When you are trying to maintain wings level slow flight are you keeping the ailerons neutral and using the rudder to control bank?

Use the rudder like you would use your hand to balance a bat or broomstick with lots of small rapid movements.

[Great Ozzie]

It also shows that the bottom of the white arc on the ASI doesn't necessarily coincide with the landing config. stall speed.

Two things to note, Nick...

1) Vso is referenced to power-off. So... a specific weight, specific c.g. (forward / aft) etc. 1g stall.

2) This is what is most important... an airplane can stall in any attitude and any airspeed. Briefly, two maneuvers that can demonstrate this (one aerobatic):

•Pitch up into the vertical, just before losing flying speed, gently nose over. The airspeed drops down to near nothing, but you are still flying. (I reckon Dudley would say something similar regarding the hammerhead, but I have not performed those). So this an "anti-example"...

•The Accelerated stall. Ok to do in our C172 / Cherokee, but I would do in the Utility category (based on weight and c.g.) @ airspeeds under what the manual specifies. More on The Accelerated Stall at this Plane & Pilot article.

How I am doing these...

•Couple thousand feet agl
•Setup 'An Approach' - 55-60kias w/ full flaps, approach power and descend a couple hundred feet
•At your chosen altitude - pull the nose up gently just like you would for landing (nose slightly above the horizon)
•Hold the altitude until the break.

Also, I have "Autorudder" enabled (twisty rudder for me too) so I reckon that gives a bit of an edge.

Oracle, as far as "definitely not watching airspeed"... amen to that! Too much going on. You can get a glance over there, but with the plane being mushy and that stall warning going, who cares what the speed is. (it's the blasted altimeter and vsi I am more concerned with). Kind of like this trim setting thing that has be talked about (that peeesh-ti! sound was me opening a can of worms). Set it for takeoff to "N" and where it goes or ends up - who cares! That is... until prior to departing again...

In one of your links Nick, you can see in one of posts by '%MAC' he references one of Kershner's pubs (On Landings) that has been talked about here. Those are very good to have.

the tachometer green arc extends to 2,700rpm so I'm guessing they're 'S' equivalents

That has been my thinking too. It certainly explains the difference and I would think that part of the prop kit.

-Rob