160 HP engine is under-powered for pontoons and amphibious

[dany93]

As several people noticed, the 160 hp-powered c172p is under-powered, which makes it "lazy" at full load. Floats and amphibious worsen everything (added drag). I tried to fiddle the propeller pitch angle, at no avail. The original one is not far from the best.

I have a test version with a 180 hp engine. On my c172-180hp branch https://github.com/dany93/c172p-detailed/tree/c172-180hp

Easy for the engine.

The propeller is much more questionable. It is the result of compromise between climbing rate, short field takeoff, and cruise or max velocity. For the propeller, I use the NACA 640 data http://naca.central.cranfield.ac.uk/reports/1938/naca-report-640.pdf. They worked rather well for DR400, DC3, Cap10B. But everything is never certain... And I refuse to cheat the values. I check their consistency, I (re-)calculate the efficiency when I extract them from the curves.

Positive:

• With default gear at full load (2400 lb), I have a 830 - 850 ft/mn climbing rate (80 KIAS).
• With amphibious at full load (2400 lb), 648 ft/mn (80 KIAS). In accordance with @tigert's data https://github.com/Juanvvc/c172p-detailed/issues/269#issuecomment-110268962

No so positive:

• The propeller (76" diameter) does not reach 2700 RPM, which means that the 180 hp are not reached during climbing. But if I decrease the pitch angle, the max air velocity will be lower than I expect. My attempt with a 78" diameter propeller makes me feel that it is not the solution (remains to be seen better).
• Levelled flight 2000 ft, 2500 RPM: with standard gears115 KIAS (hardly higher than with 160 hp). With amphibious 110 KIAS (I would have expected less, and do not know what to do).

My reasoning is that, even if this propeller is still questionable, the result is better than with the 160 hp engine. More pleasant.

[onox]

Ah, in that case you would have to do git pull --rebase master I think.

[dany93]

I don't mind, I don't understand the effect. What is the best I should do? From which branch?

[onox]

Ok, lets first update your "master" branch. Can you do that?

[onox]

The latest commit should then become Merge pull request #318 from Juanvvc/bug-311.

[dany93]

As usually (from my master branch) git pull upstream master or git pull --rebase master?

[onox]

No, git pull upstream master. (Do this in your master branch, not your c172-eng160-180hp branch)

[dany93]

OK, done. My branch: master, last commit Merge pull request #318 from Juanvvc/bug-311

[onox]

Yes, ok, now switch back to your c172-eng160-180hp branch using git checkout c172-eng160-180hp.

[onox]

And then do git pull --rebase master.

[dany93]

git pull --rebase master fatal: 'master' does not appear to be a git repository fatal: Could not read from remote repository.

Please make sure you have the correct access rights and the repository exists.```

[onox]

Sorry, git rebase master.

[dany93]

Seems OK: "Current master branch is up to date" (in French, my english translation)

[onox]

What are the two top commits? Use git log --oneline.

[dany93]

git log --oneline
8ad2589 Merge pull request #318 from Juanvvc/bug-311
c8621bc Transmit rollspeed-ms of (amphibious) gear over multiplayer

What will it do, and what should I do (or not do) later to update?

[onox]

Is this in your c172-eng160-180hp branch?

[dany93]

No, it was in my master branch.

In my c172-eng160-180hp branch:

Sur la branche c172-eng160-180hp
Votre branche est à jour avec 'origin/c172-eng160-180hp'.

rien à valider, la copie de travail est propre
dany@dellinux ~/FG/github/c172p $ git log --oneline
2f9f036 engine and propeller for 160 or 180 hp, test version
9dc86bc Merge pull request #292 from Juanvvc/bug-fix-284-and-288```

[onox]

1. Switch back to your c172-eng160-180hp branch using git checkout c172-eng160-180hp
2. Do: git rebase master

[dany93]

git status Sur la branche c172-eng160-180hp Votre branche est à jour (up to date) avec 'origin/c172-eng160-180hp'.

rien à valider, la copie de travail est propre (clean) dany@dellinux ~/FG/github/c172p $ git rebase master Premièrement, rembobinons head pour rejouer votre travail par-dessus... (firstly, let's rewind head to play your work again above it...) Application : engine and propeller for 160 or 180 hp, test version

[onox]

Ok, show me top two commits from git log --oneline again.

[onox]

@dany93 Are you having troubles? :worried:

[dany93]

a9d4b9f engine and propeller for 160 or 180 hp, test version
8ad2589 Merge pull request #318 from Juanvvc/bug-311```

[onox]

Ok. Do you see you have brought in the latest stuff from master and then put your own stuff (1 commit) on top of it?

[dany93]

Yes. But the effect? Hopefully, there was no conflict. What I should do or not do later?

[onox]

That is the effect. You put your own stuff on top of the stuff from master. Now you have the latest and greatest from master and still you have your extra 180hp engine :smile:

Ok, now try to push, it should fail. When it fails, try to push again but with --force.

[dany93]

Seems OK To https://github.com/dany93/c172p-detailed.git

• 2f9f036...a9d4b9f c172-eng160-180hp -> c172-eng160-180hp (forced update)

[onox]

Yes, compare:

1. https://github.com/dany93/c172p-detailed/commits/c172-eng160-180hp
2. https://github.com/Juanvvc/c172p-detailed/commits/master

Your branch is just 1 extra commit on top of master now.

[dany93]

I see and I understand that I have a repository with updated juanvvc and my last commit for 160-180hp above it, like if my commit had been added to juanvvc.

[onox]

Yes.

[onox]

Btw, is there a particular reason that /controls/engines/engine/master-bat is located within /controls/engines/ instead of /controls/switches/?

[dany93]

Now, for my updates from juanvvc master, as usual? And if I add a commit in c172-eng160-180hp, git push and that's all?

[onox]

If you add another commit to your c172-eng160-180hp branch, you can just do a regular git push.

[dany93]

And I understand that the current content from juanvvc which is in my c172-eng160-180hp branch will not be changed by the future updates of my master from juanvvc, true?

[onox]

No, unless you do git checkout master, git pull upstream master, git checkout c172-eng160-180hp, git rebase master again.

[onox]

That will do the same trick again that you just did.

[dany93]

OK. Thank you onox, and sorry for my ignorance.

[onox]

Don't worry, you have never done a rebase before, so I understand it may be difficult.

[onox]

Anyway, can I move controls/engines/engine/master-bat to controls/switches/master-bat? And do the same thing for master-alt?

[onox]

I'll do it in a copy of your c172-eng160-180hp branch and push it later to juanvvc repository so that you can just pull it and it will fast-forward (no merge commits).

[dany93]

Anyway, can I move controls/engines/engine/master-bat to controls/switches/master-bat? And do the same thing for master-alt?

I have no opinion, I do not understand what is does, how and why you do that. If it works from you point of view, you are better than me.

[onox]

Well, master-avionics sits already in /controls/switches/ and it might make switching between the two engines easier.

[dany93]

In fact, I was just able to do the FDM part and the fuel.xml file to give the necessary tool. Beyond that, I trust you and hope (am almost sure) you and wlbragg can make it work.

[onox]

I have your commit locally here, so we can take it from here then.

[dany93]

Do not forget that I wrote above: https://github.com/Juanvvc/c172p-detailed/issues/273#issuecomment-111828903

In the future, the engine activation can be done by one or the other of the properties:

• magnetos: /controls/engines/engine[0 or 1]/magnetos = 0 or 3 (engine[0] for 160 hp, [1] for 180 hp)
• float chamber: fdm/jsbsim/propulsion/tank[2 or 3]/priority = 0 or 1 (tank[2] for 160 hp, [3] for 180 hp).

[onox]

The procedures you mean?

[dany93]

No. The properties that can be used in your code to switch engines (unless you prefer another way) .

[onox]

I have pushed branch bug-273.

[onox]

@dany93 For the primer and throttle, we are currently using /controls/engines/engine/primer and /controls/engines/engine/throttle, but it seems we can move these out of /controls/engines/engine[0] as well, right?

Although we can probably keep them there (and use them for both engines)

[dany93]

I do not understand, cannot respond. It seems that the originals are by default. And I don't see neither the consequences, nor why. Merely, try to keep the code understandable for the future developpers.

What can I do with https://github.com/Juanvvc/c172p-detailed/commits/bug-273 ?

[onox]

Another question: If I set /controls/engines/engine[1]/magnetos to 1, 2, 3, does that mean I must set /controls/engines/engine[0]/magnetos to 0?

[onox]

I don't quite yet understand which code is reading /controls/engines/engine[1]/magnetos.