amateur built floatplane question

[digits_]

Can you really trust your airspeed doing a side slip?

Certainly not near the stall! A reference to the IAS to CAS tables is pretty important, and there is a likelihood of additional error from the yaw, which is not documented.

Wouldn't a sideslip always cause your speed to underread? Your pitot pressure would go down, your static pressure would increase, thus the difference would be lower than it would be in coordinated flight.

So the speed would be wrong, but it would be 'on the safe side' of wrong.

[Bede]

Can you really trust your airspeed doing a side slip?

Certainly not near the stall! A reference to the IAS to CAS tables is pretty important, and there is a likelihood of additional error from the yaw, which is not documented.

Wouldn't a sideslip always cause your speed to underread? Your pitot pressure would go down, your static pressure would increase, thus the difference would be lower than it would be in coordinated flight.

So the speed would be wrong, but it would be 'on the safe side' of wrong.

No. It depends on the side of the static port and which way you're slipping.

[photofly]

TeePee - If I've planted a little doubt in someones mind about side slipping a float plane or ski plane on short final I'm happy. Don't ask me about the theory of the whole thing all I know is the Cessna I was flying shook me up and I'll never do it again.

Was it skis, or floats? Or was it a function of that particular model of Cessna?

I'm also confused.

[digits_]

Certainly not near the stall! A reference to the IAS to CAS tables is pretty important, and there is a likelihood of additional error from the yaw, which is not documented.

Wouldn't a sideslip always cause your speed to underread? Your pitot pressure would go down, your static pressure would increase, thus the difference would be lower than it would be in coordinated flight.

So the speed would be wrong, but it would be 'on the safe side' of wrong.

No. It depends on the side of the static port and which way you're slipping.

Good point.

If you slip in a way such the static port is shielded, you could have some negative pressure on that side, but you'd still have your static port out of wind as well. Would there be a scenario where the negative pressure would be greater than the loss of dynamic pressure?

[Bede]

Wouldn't a sideslip always cause your speed to underread? Your pitot pressure would go down, your static pressure would increase, thus the difference would be lower than it would be in coordinated flight.

So the speed would be wrong, but it would be 'on the safe side' of wrong.

No. It depends on the side of the static port and which way you're slipping.

Good point.

If you slip in a way such the static port is shielded, you could have some negative pressure on that side, but you'd still have your static port out of wind as well. Would there be a scenario where the negative pressure would be greater than the loss of dynamic pressure?

If your plane is yawing greater than 45 degrees. Otherwise, no.

[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 4208 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.