Cessna 172 glide ratio

  • I've always felt the original Aerofly 172 was somewhat lightweight. Recently, I started playing with the .tmd file, and was able to increase weight to the maximum (2550 lb), adding weight to fuselage and wings (106kg to fuselage and 32,5kg on each wing, representing a full load of 52gals). I'm very pleased, as it flies more similar to how I fly the real 172. However I still believe the Aerofly 172 has a much lower glide ratio compared to the real one, especially with full flaps (I'm comparing to a 172sp, not the old ones with 40° flaps). I would really like to find a way to change it, as it makes approaches, especially circuits, considerable less realistic (e.g. if you are too high on the glidepath, on Aerofly, you just add full flaps and you're all set, while the real one requires more discipline to manage energy), the same applies for flaring, the real one likes to float on the runway, while the Aerofly one drops like a brick. I fly Aerofly in VR always before flying in real life, and the difference in glide performance is very noticeable.


    Is there any parameter(s) to alter this behavior? Thank you!

  • Thank you!, I played a bit with the values, It seems the CdFlap value is extraordinarily high, by default is set to 0,4 on the 172. The wiki recommends 0,06 for slotted flaps, such as the C172 (there seems to be some discussion on what kind of flaps does the Cessna have, however the manual refers it as "single-slot type wing flaps")

    Had a quick flight with 0,1 and the difference was substantial, the plane behaved much more realistically on approach, I'll play around with other values.


    Is there a reason to use such a large value?



    Table of flap coefficients

    Recommended values for the Aerofly are:

    Type of flapClFlapCdFlapCmFlap
    Plain flap2.10.0-0.2 … -0.5
    Split flap2.40.2-0.2 … -0.9
    Slotted flap2.70.06-0.2
    Fowler flap2.7 … 3.40.2-0.6 … -1.1
  • Out of curiosity, if I understand correctly you're saying that the default C172 glide distance is too low, correct? I'm really interested in your findings because a friend of mine who recently got his PPL in a C172 once told me how he was practicing engine failure emergencies with his flight instructor by cutting the throttle on downwind and then had to return to the runway while gliding, and I was never able to recreate this procedure in Aerofly because the C172 dropped like a rock once I pulled the throttle all the way back. I asked on this forum if this was a mistake and was told off for having no idea how a C172 is not a glider and so on.... but your post suggests that there really might be a unrealistic value in the tmd file. I'm looking forward to what you'll find out about how the gliding performance changes with different values for the Flaps settings.

  • Keep in mind that the real world cessna also glides different if you just idle the engine or when you actually shut it down and the prop stops. If the prop is rotating at idle it creates more drag. If you only practice emergencies with engine at idle it may not be representative of an actual engine failure. I would suggest trying both with a flight instructor on a long enough runway so that you can land long without running out of runway...


    I actually have a Cessna mod with different flight characteristics: https://www.aerofly-sim.de/dow…oflyfs2/af2_c172_download

    Please give it a try and provide feeback so that I can correct things like this.

    If my modded cessna flies exactly like it should, then we can think about changing the default cessna to that setting.

  • When I was teaching primary flight training, many years ago, I always, without exception, introduced the student to accelerated stalls and recovery and engine out procedures, usually with the flight ending up on a deserted highway or large pasture. It was usually several years later when I got a note, a letter or a phone call thanking me for teaching these potentially life saving techniques although neither are required for getting the PPL.

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    Out now: Hawaiian Islands 8) Part 1: Kauai + Niihau v2

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  • Keep in mind that the real world cessna also glides different if you just idle the engine or when you actually shut it down and the prop stops. If the prop is rotating at idle it creates more drag. If you only practice emergencies with engine at idle it may not be representative of an actual engine failure. I would suggest trying both with a flight instructor on a long enough runway so that you can land long without running out of runway...


    I actually have a Cessna mod with different flight characteristics: https://www.aerofly-sim.de/dow…oflyfs2/af2_c172_download

    Please give it a try and provide feeback so that I can correct things like this.

    If my modded cessna flies exactly like it should, then we can think about changing the default cessna to that setting.

    I'll try the mod and report back, though I lost my only real world flying reference because my friend moved to Switzerland a few months ago so I can't let him try the different tmd settings and ask which one he deems the most realistic.

    On another note, does the prop really stop at an engine out failure? Depending on the cause of the failure wouldn't it be possible that it keeps spinning because of the airflow going over it, unless you have a prop pitch lever that lets you feather the prop, which the C172 doesn't have if I'm not mistaken? This is a question to the real world pilots out there because I obviously don't have any real experience with these situations.

  • On another note, does the prop really stop at an engine out failure?

    Depending on the engine and it's compression; but yes. Many years ago we have been flying the C-Falke a lot and also with engine out. You had just to fly a bit slower and the prop stopped. The rotax engine stops basically right away after engine off. With a Lycoming/Conti I don't have experience (and I'm not too keen on it..), but out of my feeling it should be easy to get the prop to a stop.


    One more note from my side regarding the flaps; I have some 50-60 h on the SP and IMHO comes the Aerofly pretty close to the real one. The flaps are hell of effective, you can almost dive into the airport. Unlike, for example, the PA28 where you need to do an much flatter approach.


    Cheers,

    Kai

  • Yes, when you dont fly 150 knots :) :) Propeller stops in Cessna and so on ...


    For my training, i always make landings from 2000ft with STOPed

    Propeller with all Ultralights + Planes + Motorgliders + Gyro + Trike und Paramotors :)


    No one rotate (fast) in glide-path ...only when you put stick to the front and fly really fast ...then ...

    sometimes engines starts ( when ignition is on ).




    and many more ...

  • Well, I'd not be so definite : of all my engine out practice with Lycoming engines (mostly DR400) my experience is you have to slow down to quite low speeds to stop the prop... at 80kts (best glide speed for the Robin) the prop keeps windmilling.

    It much depends on engine and prop...


    BTW:

    One aspect that is usually poorely rendered in flight simulators is the rather long delay between action on a fuel selector and effect on the engine.

    During PPL basinc training my instructor would occasionnaly shut off the selector while asking me to identify the name of that village on the left, to test my actions. The engine keeps running for a quite a few seconds before to cough and shut down.

    After failure processing, we would switch back on the fuel selector, wait for engine to restart and continue the failure exercise with throttle cut...


    On the opposite, some aircraft in our fleet have 2 additional 40 liters wing tanks. When flying long range and if I have enough ground clearance I like to use them until they run totally out of gas - there's no point in leaving 5 liters in them that you won't be able to use in case you are a little bit short...

    So the gauges indicate zero for several minutes (up to 10 minutes actually !), and you never know when the engine will suddenly run out until it suddenly happens.


    The procedure may differ from an aircraft to the other, for the DR400 you turn on the electrical pump and switch the fuel selector to the desired tank and wait keeping level flight until airspeed drops to best glide speed, then you let the aircraft glide down keeping best glide speed (80kt clean).

    I never did it with a stop watch in the hands so far, but I'd say it can last some 30 seconds, maybe more, with the prop windmilling until the engine restarts... I can tell you, with the engine out it feels like an eternity!

    So never do it without enough ground clearance...

    If the prop would stop mindmilling it's even worse since you don't know when the engine is ready to restart...


    My 2 cents...


    Cheers

    Antoine

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  • Very interesting Antoine. I grew up doing a lot of solo flying over and around sand bars and shallow water as the wide and shallow rivers of central Florida dried up each summer. Each day revealed a new or different fishing hole or place the walk in the warm water no more than a few inches deep.


    These were fun times for practicing full landings with the prop usually stopped. This was as close to gliding as we got for a long time. Eventually, a gliding school was established with 2 gliders and a tow plane. I thought my Cessna 150 was as quiet as the S-222 in those days. I would turn off the engine at say 5,000 feet and pick a sand bar as my touchdown spot and enjoy the ride down.


    I never ran out of gas or landed gear up, but I did come close a few times.


    Thanks for the memories.

    A steely-eyed Sierra Hotel record setting F-15E Strike Eagle simulator pilot. 8o
    Out now: Hawaiian Islands 8) Part 1: Kauai + Niihau v2

    Work in Progress: Part 2: Molokai, Maui, Lanai, Kohoolawe + Molokini Crater



  • And would you say that the gliding behavior of say the Aerofly C172 is realistic? I have absolutely no real life experience with this but I was always under the impression that GA aircraft, unlike fighter jets, as a rule are designed for benign behavior in emergency situations that gives the pilot a chance to resolve the problem before something bad happens. I thought that included things like relatively easy stall recovery and at least some basic gliding capabilities in case of a engine out failure. At least that was what my friend told me when he was practicing these procedures. In Aerofly I have the feeling that the GA planes like the C172 or the Just Flight C152 drop like a rock when I set the engine to idle or when cut the mixture in flight, but maybe that's just from my lack of real world experience. I also thought that the real world Piper PA28 that my friend's FI once landed with me on the right front seat had a landing flare that seemed to last forever, while in Aerofly I habe difficulties to get into a decent flare before hitting the ground, but of course that might also be the difference between a low wing and high wing aircraft.

  • And would you say that the gliding behavior of say the Aerofly C172 is realistic? I

    I don't fly much Cessna either IRL or in flight sims. My sole Cessna experience IRL gave me the feeling you apply a large amount of aileron in one direction and wait patiently for something to happen...


    Aircraft like Robin DR400 have a glide ratio >9, meaning that it glides much better than most pilots would expect while practicing emergency landings. My meager experience with Cessna gave me the feeling it'd drop like a stone in comparison, but the glide ratio is still about 9, so you can travel horizontally 9 times your height AGL...


    Cheers

    Antoine

    Config : i7 6900K - 20MB currently set at 3.20GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.

  • Very interesting Antoine. I grew up doing a lot of solo flying over and around sand bars and shallow water as the wide and shallow rivers of central Florida dried up each summer. Each day revealed a new or different fishing hole or place the walk in the warm water no more than a few inches deep.


    These were fun times for practicing full landings with the prop usually stopped. This was as close to gliding as we got for a long time. Eventually, a gliding school was established with 2 gliders and a tow plane. I thought my Cessna 150 was as quiet as the S-222 in those days. I would turn off the engine at say 5,000 feet and pick a sand bar as my touchdown spot and enjoy the ride down.


    I never ran out of gas or landed gear up, but I did come close a few times.


    Thanks for the memories.

    Wow, this remembers me a jaw dropping section in Canadian air laws stating that expect for specific places listed in a document, all of Canada can basically be considered as an aerodrome...


    I think practicing emergencies down to actually landing is an extremely valuable experience I'm lacking. Around here, the sole places out of aifields where you might hope landing without damaging the aircraft are some seldom very clean fields (you'd hence destroy harvest) or large roads, meaning unacceptable hazzard for traffic, not to mention obstacles like powerlines, road signs, street lights, etc.

    So while pratcicing we always go around just before actually touching down, except when practicing over an airfield.


    I ever felt like the day one really has to emergency land in a field, one of the big dangers is to loose control before touchdown while afraid of being too fast. Glider pilots have that experience of full landing in the middle of nowhere and I'm sure that's a real help in case of emergency.


    Cheers

    Antoine

    Config : i7 6900K - 20MB currently set at 3.20GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.

  • The only time that I lost an engine in a single engine airplane for real I had just entered the traffic pattern for landing at a fairly busy executive airport in Orlando Florida. The prop stopped immediately and I chose to land on a taxiway just so I would not stop traffic for an hour or so. The FAA said that was a "very smart thought" when I file the report. It was a rental Cessna 172 and I had about 150 hours in Cessnas as the time.


    I had plenty of gas and everything seemed normal. I never heard if they found why the engine stopped.

    A steely-eyed Sierra Hotel record setting F-15E Strike Eagle simulator pilot. 8o
    Out now: Hawaiian Islands 8) Part 1: Kauai + Niihau v2

    Work in Progress: Part 2: Molokai, Maui, Lanai, Kohoolawe + Molokini Crater



  • A local lady that died a few months ago wanted Mary and me to write a book about our lives. She had known me since the Apollo days and wrote articles for our local hometown weekly paper most of her life. We declined with the reason that most folks would consider it fiction.


    Regards,

    Ray

    A steely-eyed Sierra Hotel record setting F-15E Strike Eagle simulator pilot. 8o
    Out now: Hawaiian Islands 8) Part 1: Kauai + Niihau v2

    Work in Progress: Part 2: Molokai, Maui, Lanai, Kohoolawe + Molokini Crater



  • Ray has so many stories to tell from his life! It's always a pleasure to read them, I really love this. Thanks Ray :)

    Yes, it’s always been a delight to read

    Config : i7 6900K - 20MB currently set at 3.20GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.

  • And would you say that the gliding behavior of say the Aerofly C172 is realistic? I have absolutely no real life experience with this but I was always under the impression that GA aircraft, unlike fighter jets, as a rule are designed for benign behavior in emergency situations that gives the pilot a chance to resolve the problem before something bad happens. I thought that included things like relatively easy stall recovery and at least some basic gliding capabilities in case of a engine out failure. At least that was what my friend told me when he was practicing these procedures. In Aerofly I have the feeling that the GA planes like the C172 or the Just Flight C152 drop like a rock when I set the engine to idle or when cut the mixture in flight, but maybe that's just from my lack of real world experience. I also thought that the real world Piper PA28 that my friend's FI once landed with me on the right front seat had a landing flare that seemed to last forever, while in Aerofly I habe difficulties to get into a decent flare before hitting the ground, but of course that might also be the difference between a low wing and high wing aircraft.

    you are absolutely right. They drop like a rock. I flew C172 in real life, on a power off (idle) approach you have to use flaps in order to get down this bird and if you put it late, then you have a last chance doing side slip and many time you only chance is to go around because you wasn’t able to reach the first third of the runway. I am hoping so much the Aerofly team could correct this soon. If you can, try a payware c172 in x plane 11, do it! (REP C172 or Airfoillabs) I flew a pattern in vr and it was like flying the real cessna!!


    Besides Its very simple to make a comparison, grab a power off landing in hd in youtube and take a look at the vertical speed indicator, the cessna glide around 600 fpm, on turns increase to around 900.