amateur built floatplane question

[photofly]

If you want to see the effect of a side slip angle on the static pressure, look for sudden altitude fluctuations on the altimeter and indications of rapid climbs/descents on the VSI as you slip. If you don’t see any, the pressure in the static line isn’t affected.

I think this (“Gracey”) is the standard place to start for anyone interested in errors in pressure measurements in flight. Chapter 4 looks relevant, particularly:
https://ntrs.nasa.gov/api/citations/198 ... hment=true

Here’s a bit to whet your appetite…

C9581303-21E5-47B4-928F-A085AA43B178.jpeg (180.59 KiB) Viewed 11651 times

If you wonder why your pitot tube has a bullet shaped nose, here’s the answer: it’s very insensitive to angle errors (see figure 4.7) - essentially zero error in sideslips up to 20 degrees, which is more than you’re likely to obtain.

[ruddersup?]

Like some 172's, the 170B has the outboard end of the flap coincidentally located such that in a slip, a wake off the extended flap can burble over the horizontal tail, and momentarily reduce its effectiveness. It is a thing, and I have done it a number of times. That's why some 172's are placarded to avoid slips with flaps extended. During certification, it was deemed to be acceptable (so no "prohibited"), but I agree, it can catch a pilot unaware on a calm day.

I stand vindicated - thanks PilotDAR.
I must admit that with all the years flying floats commercially, I have never had to side slip. We are talking small lakes like in very.
With flaps and floats I wonder if you should be carrying passengers at all if you must side slip too.
Anyway we are off topic - going back to studying rudderlets.

You guys can continue on with saying its just normal operations.

[PilotDAR]

With flaps and floats I wonder if you should be carrying passengers at all if you must side slip too.

A flap equipped floatplane probably does not need to be slipped for any landing you plane to take off from. And yes, I avoid slips with passengers, it can annoy them. But, that does not mean that slips can be a useful technique to tuck into a really tight spot precisely if you have an engine failure.

The choice to not slip in normal operations does not condemn the technique to being a bad idea, just a technique with specific uses.

As for a ventral fin, or finlets on the H stab, perhaps your plane would benefit from them. I can say from experience that the testing you'll need to do to know for sure really should involve slips, it's part of the testing....

[ruddersup?]

As for a ventral fin, or finlets on the H stab, perhaps your plane would benefit from them. I can say from experience that the testing you'll need to do to know for sure really should involve slips, it's part of the testing....
---------- ADS -----------
Sooooo I test a side slip on floats with flaps extended. If I'm alive after then all is well, huh? So what would be a failure of a side slip? Loss of elevator authority? Entering a spin or spiral dive or snap roll? Don't take me seriously, please.

[PilotDAR]

Sooooo I test a side slip on floats with flaps extended

The choice really is yours, you asked. If you choose not to test under controlled conditions you select, then could be one day you get a gust from the side on final, you step on a pedal out of instinct, and find out then how it flies in that configuration.

For certified planes, there is a prescribed group of flight characteristics to be tested, and confirmed. if the plane won't pass all of them, it will not be certified. This list is based upon a lot of experience, some of it bad. So I take it to heart, and assure that if I have test flown a plane, it has shown compliance to all of the requirements.

So what would be a failure of a side slip? Loss of elevator authority? Entering a spin or spiral dive or snap roll?

'Could be. If it is to be, best find out during testing. Yes, I have had planes do all of those things during testing, sometimes as planned, a few times as a surprise. A few times I have returned the plane, and said "Not good enough". Honestly, it is a situation of lack of, or inadequate, control which worries me most. When you run out of control, you have to get imaginative quickly. Of course, snap rolls are a poor idea in a non aerobatic airplane, but it can happen ('did one flight testing a Lake Amphib with an engine change, while attempting to enter a one turn spin). If an incipient spin entry or spiral at altitude absolutely terrify you, you should have more confidence with the directional stability and control of your airplane ..... the entry to this topic.

I have not flown the genre of airplane you describe, so can only compare what I'd guess its handling would be, to a very light certified plane.

[Bede]

With flaps and floats I wonder if you should be carrying passengers at all if you must side slip too.

A flap equipped floatplane probably does not need to be slipped for any landing you plane to take off from. And yes, I avoid slips with passengers, it can annoy them. But, that does not mean that slips can be a useful technique to tuck into a really tight spot precisely if you have an engine failure.

I disagree. There's a lake I went into recently with a guy with a fishing camp in the Thunder Bay area. One end has hills and windmills. (I never realized how massive those things are.) With a south wind, you have to slip to get in, but getting out is relatively easy because of the valley and creek.

Most float planes don't require slipping (drag from floats is high enough). The Citabria glides well with floats so you end up slipping often, even with flaps.

[TeePeeCreeper]

Ruddersup?,

You have me utterly confused. Anyone whom has extensive -2 experience knows that full landing flap landings will result in a torque roll if max power is applied in the event of a go-around. “ I've done it hundreds of times but in certain situations” I take it you’ve gotten lucky in not having to do one?

(Try it at ‘5000 feet in a landing config with full flap for yourself if you don’t believe me )

All the while advocating a non slip methodology at the same time…. I don’t get that nor do I understand advocating that a C170 shouldn’t be slipped… ever. (Bless the 170 a docile and very stable ship to begin with!)

I realize this is off topic to your original question but my little enquiring mind wants to know!

Regards,

TPC

[PilotDAR]

-2 experience knows that full landing flap landings will result in a torque roll if max power is applied in the event of a go-around.

forgive my thread drift. I've only flown Beavers for a few hours. Is it not correct that full flap is not a flight setting, and only for sailing or emergency short landings? I've never used full flap in the Beaver, only landing flap. I did slip the Beavers I have flown out to full pedal, I was flight testing them.

[ruddersup?]

Read my lips TeePee - IMHO don't slip on floats (especially when carrying a boat or canoe or is it ok then too) or skis. You have an opinion but I've experienced an unexpected moment that when side slipping a Cessna 170 on wheel skis. You know what they are, huh? Ask PilotDAR about unexpected happenings. Done this many time soooooo - oops. They just happens. Maybe a screw up handling the bird but we all aren't perfect. On wheels have a go at it but respect what has been added on since certification. There are surprises lurking on every aircraft the more you modify them.
Beaver - not sure what you are hinting at there -

[PilotDAR]

There are surprises lurking on every aircraft the more you modify them.

Not certified airplanes following STC'd modifications, that's why they're being re test flown during the mod approval process. No surprises, once approved. Even the less than ideal 172 slips with flaps extended was deemed acceptable by the FAA during certification - not ideal, but acceptable. A certified plane has demonstrated compliance to get the approval. If there are unapproved modifications/external loads, then it's not really certified anymore, and the pilot is on their own!

The surprises you allude to may be found in combining modifications. A wise owner follows the process for that, and has the desired combination of mods tested and approved. I have done serialized STC's which do nothing other than to approve the combination of several STC'd mods. I approved them because they were found to be compliant, following demonstration during flight testing.

As the pilot, you may choose to not slip a plane, and that's fine, but it doesn't mean that the plane is not capable. The certified plane, in its compliant configuration is capable, or it would not be certified that way. If you think that you have found a certified airplane which is not compliant, I hope that you snagged it, and notified the owner to have the deficiency investigated!

You started the thread by asking an entirely appropriate question about a modification (which I understand to be to a non certified airplane). For my limited understanding, a determination must still be made for non certified planes, though not in the STC format, that that modification is safe. I know what the test procedures would be were it to be certified, I can't see a good reason to have a much different pass/fail criteria for an uncertified plane, it should still fly well, and be tolerant of some non standard handling.

[TeePeeCreeper]

-2 experience knows that full landing flap landings will result in a torque roll if max power is applied in the event of a go-around.

forgive my thread drift. I've only flown Beavers for a few hours. Is it not correct that full flap is not a flight setting, and only for sailing or emergency short landings? I've never used full flap in the Beaver, only landing flap. I did slip the Beavers I have flown out to full pedal, I was flight testing them.

We are over due for that breakfast/lunch!

Ruddersup?,

I mean’t no offence nor do I wish to spar. With that said, you brought up the whole full flap landings (as I appropriately quoted you above) and you are now bringing external loads into the mix? A red herring perhaps?

Maybe I read your posts the wrong way? Regardless, I am really curious… what kind of OM mod are you seeking to achieve testing on a buck 70 with?

Regards,

TPC

[ruddersup?]

Pleasant Sunday morning chat, strong crosswind drifting us off topic.

TeePee - I'm not modifying a Cessna 170 on wheel skis - my event, in that aircraft, happened probably 20 years before you were born but that result has left an impression.
Whatever you do close to the ground other than straight and level, I hope you are thinking is this necessary. It's easy enough to crash straight and level never mind throwing the bird around. I'll continue to argue that a floatplane with flaps will get into any lake more safely and just as short as adding a side
to the approach. Just thinking dropping in over the trees in a side slip and losing the wind and geez no flair, hmmm.

I've lost several friends throwing aircraft around, close to the ground, who were great pilots in manouvers approved for the aircraft.

PilotDAR - Your accident was because you were doing a manouver not approved in a certified aircraft or just a screw up in a normal approach?

PilotDAR -I also would argue, lol, that STC's can be getting out of hand. It's not unusual to have an aircraft with a dozen add on STC's (or more) and who is approving all this - the AME installing them? Believe me, I ARE ONE. No one is watching what is going - but pilot owners want them because they think they will help performance - not necessarily true. Sometimes the original aircraft is hard to beat - and exactly what are you trying to achieve?
Craziest STC IMHO is the flap gap sealsl on a Cessna 185 floatplane - who in hell approved that? Probably approved on wheels and then somehow got put on floatplanes after someone said, ahhhh, this should be okay. I did call TCCA and they said it's good to go, hmmm.

Now to enjoy my morning coffee.

[PilotDAR]

It's not unusual to have an aircraft with a dozen add on STC's (or more) and who is approving all this - the AME installing them? Believe me, I ARE ONE. No one is watching what is going

Every MAE who signs on an STC, signs for the following - it's right on every certificate:

Prior to incorporating this modification, the installer shall establish that the interrelationship between this change and any other modification(s) incorporated will not adversely affect the airworthiness of the modified product.

That requirement, in the context of Standard 571, Appendix A:

(d) Performance and Flight Characteristics

Does the modification or repair involve alterations that:

(1) significantly increase drag or exceed aerodynamic smoothness limits?

(2) significantly alter thrust or power output?

(3) affect stability or controllability?

(4) induce flutter or vibration?

(5) affect the stall characteristics?

Means that the AME is responsible, as always, for having the data which says that two (or more) otherwise unrelated STC's are compatible. In the absence of that data, the AME must obtain it, most commonly by seeking a serialized STC for the plane, which links the STC's to each other. I have done many sSTC's which do nothing other than approve STC'd mods together on one plane. My record was a 182, from plain Jane to amohib with 27 STC'd mods combined. Nearly 30 hours of development and flight testing, including taking a TC Test Pilot for his evaluation of some of the mods.

A few years back I was asked to approve an AoA system on a C 206H with other wing mods. In doing the flight testing, and following the installation instructions for the AoA system, I found an unsafe condition. After consultation with the AoA manufacturer, I offset a set point for the AoA, and the plane was entirely safe. I issued the sSTC, and then reported what I'd learned to TC. 5.5 hours of set up and test flying to make a safe, and approvable plane.

Yes, combining mods can result in unintended characteristics, Owners are being responsible by having the whole job done properly, including the research, and possible approval of multi mods. AME's are being thorough when they assure that they have the data for the mods they are doing/combining. Pilots are being responsible when they are assuring that their operations, and external loads that they might carry are within the approved limitations for the plane.

If in doubt, stop and ask - which is the opening theme of this thread....

As for the accident I was in, I was PNF, finishing a float rating for a skilled pilot, in ideal conditions. Something went wrong, and I can report that I simply do not recall what. I remember going from looking out to the right, thinking, we're going to touch..... now... and we touched nicely, to waking up in hospital four days later. Only lesson learned, when right seat PNF, look forward during landings, not out to the side, no matter how confident you are about the skill of the other pilot!

[ruddersup?]

PilotDAR - what world are you living in?

Would be nice if the whole industry complied like you suggest must, but.......... I would think that there is not an aircraft flying that meets regulations 100% - the industry would be grounded in a heartbeat if that were true.

I wonder if everyone flew the aircraft the way it's supposed to be flown then no one dies?

I disagree with you saying you were PNF. Giving out a rating would require you to not allow the aircraft to ever get into an event that happened to you.
If you are a qualified flight instructor you should understand that. If the plane crashes it's the instructor's fault - nothing to argue there but if the tail falls off then I'll listen to your side.

I keep saying "I" so don't take me too seriously.

Morning chores done, quick coffee then practise my side slips (on my bicycle).

[PilotDAR]

Giving out a rating would require you to not allow the aircraft to ever get into an event that happened to you.

I can't disagree with that. We were landing to the dock, so I could get out, and send him for his five solo circuits. He was not as ready as I should have assured. Lesson learned, and I have not done float training since.

I would think that there is not an aircraft flying that meets regulations 100% - the industry would be grounded in a heartbeat if that were true.

Sadly, I agree with you on that...

Would be nice if the whole industry complied like you suggest must,

Yes. It starts with the owners requesting, and paying for compliant maintenance and modification to their airplanes. Then it's up to the properly empowered, and instructed AME to do the whole task, and be paid for their time to do a thorough job of it. Then, in the case of aerodynamic mods, or alterations requiring verification of adjustment, or characteristics, the plane should be test flown by a pilot familiar with the type.

As more mods become available, and owners seek to "modernize" their planes, rather than shopping for something new, there will be more and more opportunity for mod combinations to cause unfavourable interactions. It'll be more and more important for AME's to know what to look for, and be thorough about assuring airworthiness.

[Bede]

Whatever you do close to the ground other than straight and level, I hope you are thinking is this necessary.

I'm rarely in level flight close to the ground. I'm usually descending on landing.

Would be nice if the whole industry complied like you suggest must, but.......... I would think that there is not an aircraft flying that meets regulations 100%

Mine does.

the industry would be grounded in a heartbeat if that were true.

If that's the case, then maybe it should.

I disagree with you saying you were PNF. Giving out a rating would require you to not allow the aircraft to ever get into an event that happened to you.
If you are a qualified flight instructor you should understand that. If the plane crashes it's the instructor's fault - nothing to argue there but if the tail falls off then I'll listen to your side.

I'm an instructor too and I've seen how fast someone can do something unexpected and there is nothing you can do. PilotDAR is probably the most helpful & knowledgeable guy on this forum. To rub his face in something crappy that happened is beyond the pale. You come on here, ask for advice, helpful advice is given by knowledgable people, and then you turn on the people who have more expertise than you (you were the one asking the questions, remember). PilotDAR's too classy to call you out on your douchbaggery, but I'm not: you're an asshole.

[ruddersup?]

Bede - Everything I've said is IMHO. I did not call him out as you suggest. It's goes with the territory that the instructor has control of the situation. Ask an insurance company.
Incidentally I have known Jim longer than you have probably been alive and he has been to my facility many times. As a matter of fact I'm hoping to hire his services but please don't tell him.
All said is educational for people who do not beat their chest so delete this whole thread, it's not suitable for you.
Your age is showing - try to show some class, son.

[Bede]

Your age is showing - try to show some class, son.

OK Boomer

[rigpiggy]

Has anyone tried the inboard end plates on the ailerons as a way to increase roll stability?

[Delta22]

just to piggy-back on this forum, I know that the Beech model 18 had floats and therefore had a ventral fin added for the extra stability (something I didn't know until coming to this forum) but one thing I wonder is:
would it be feasible to instead increase the size of the vertical stabilizers on the Model 18, as its a twin tail aircraft?

alternatively, what would happen if you were to create a flying boat based on the Model 18 design? Would you *have* to increase the fin size, as there isn't really the potential to add a ventral fin.

(this is all hypothetical)

[photofly]

Ventral (and dorsal) fins have a low aspect ratio and provide slip-yaw coupling at high side slip angles, angles where the vertical stabilizer would be stalled.

[PilotDAR]

Increased vertical surface area is commonly needed to offset the aerodynamic effect of the forward portion of the floats. In Cessna 180 series planes, water rudder system friction also can effect the freedom of the rudder to move, and return to center when released (directional stability). A directionally unstable plane is simply unpleasant to fly, and can be spin prone during the approach to a stall.

You cannot assume that the structure of the airplane (and in the case of the Beech 18, the H stab) is adequate to carry the additional loads which could result from increasing the V stab(s) height. Remember that if this vertical surface is added, the loads that surface could generate will be transmitted into the fuselage, and must be safely carried.

The addition of a ventral fin is generally a structural easy do, and if you have the damage a flying surface, that'd be the easiest and least costly to replace. H stabs sometimes have finlets added, which is generally okay, though can add some complexity around elevator moving parts, and I have known them to hum in flight, which is not great for fatigue of structure.

If this characteristic of a plane is inadequate, to a point, pilot effort and skill can mask the negative handling, but manufacturers (like Cessna) tend to do the testing to optimize this. I have test flown a couple of modified C 180 and 185 floatplanes where the ventral/dorsal fin set up was wrong, and they were a misery, with one being so bad, it was truly unsafe, and I "watered" it after the first flight, until changes were made.

[ruddersup?]

On previous post we got off topic and discussed slipping with flaps. I argued, no.
There was support to slip, and why not because the aircraft had to demonstrate it for certification, hmmmm.
Well here is a link that tells you why not. I experienced the same thing in a 170 and if I was 100 feet lower I would not have survived. I had wheel skis on the aircraft. Not happy to bring this subject up again but this accident is certainly an eye opener. Supporting something like I've tried without duplication is, well .........

https://www.youtube.com/watch?v=W6wqERKBTKM

[ruddersup?]

I hate to harp on this topic but as mentioned by others there are surprises and just think about what you are attempting to do and if it is necessary close to the ground.

https://www.youtube.com/watch?v=W6wqERKBTKM

[rigpiggy]

Every float pilot thinks they need a bigger VS I have an Avid Magnum on floats. It has a ventral fin and it still isn't enough IMO.

You can check out the books by Daniel Raymer. Here's a link to information from Chris Heinz: http://www.zenithair.com/kit-data/ht.html see the one on the Horizontal Tail. It's the same principle for the VS though.

I have a book at home that has the information, but alas, I am not at home. I'll see what I can find when I get home if you need more info.

Here's what I would do: Figure out your VS volume* (VS area * wing area / distance from center of lift (wing) to center of lift (tail) * MAC) - see Heinz formula. Now try to figure out what this "volume" would be for your floats. Now design a ventral fin with the same tail volume as the "float tail volume". My guess is that this ventral fin will be way bigger than what you want so there will be a size/stability trade-off.

The other thing that you can do is look at existing floatplanes and see what increase of tail volume (in percent) that they use and design a ventral fin with that % increase in tail volume.

A lot of this is trial and error BTW, but this will get you started.

Good Luck!

*Don't get confused by "volume" as height x width x length. Tail volume is called that because when you work out the dimensions you end up with units^3 - same as a conventional volume.

has anyone used a v strake mounted to the tailwheel spring hookups