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Search: Posts Made By: Cumulo
Forum: RV-10 05-09-2022, 07:46 PM
Replies: 26
Views: 5,196
Posted By Cumulo
Flying with no data to please the lawyers?

So, are the guys that race these things having a lot of probs with flutter?

If so, lets hear it. Aren't they racing up in the high 200's I suspect that the relatively short winged RV's would have...
Forum: Propellers 02-16-2022, 03:49 PM
Replies: 16
Views: 1,523
Posted By Cumulo
std adj

This A&P has used the following procedure which I think is consistent with most CS prop manufacturers instructions and should be mentioned here.

With this routine you can easily set numbers similar...
Forum: COMM 02-14-2022, 02:44 AM
Replies: 34
Views: 3,668
Posted By Cumulo
OK, elaboration follows: ;-) The instrument...

OK, elaboration follows: ;-)

The instrument your Ham friend used looks like a somewhat upscale NanoVNA, good device for this application.

The three traces of the 2nd plot look like impedance,...
Forum: Traditional Aircraft Engines 01-29-2022, 11:20 PM
Replies: 11
Views: 1,561
Posted By Cumulo
No. An engine drowning in fuel to the point of...

No.

An engine drowning in fuel to the point of roughness and 200 rpm down is in need of attention.

2300 rpm rather than 2500 rpm, say, represents a 15% loss of torque, 23% loss of power.

Also,...
Forum: COMM 01-29-2022, 05:24 AM
Replies: 6
Views: 909
Posted By Cumulo
Good news

If the fitting will work mechanically, the ferrule, the cable - 50 or 75 ohms for the fitting will have no measurable effect at ~100 mhz, period.

I think using a bulkhead fitting to connect is a...
Forum: RV-9/9A 11-23-2021, 02:43 AM
Replies: 47
Views: 6,240
Posted By Cumulo
Hum. General characteristics of most...

Hum. General characteristics of most airplanes:
Slips are relatively benign. Even if you are nibbling on a stall in a slip, the plane will break "over the top" towards wings level allowing even low...
Forum: Engine Monitors 11-18-2021, 06:24 PM
Replies: 15
Views: 1,942
Posted By Cumulo
Well, looks like they have made a change. The doc...

Well, looks like they have made a change. The doc for the 350 on their website is updated to 2021 and shows a solid state 3 wire oil pressure...
Forum: Engine Monitors 11-18-2021, 05:01 PM
Replies: 15
Views: 1,942
Posted By Cumulo
Yep, looks like it. The on-line install for the...

Yep, looks like it. The on-line install for the 730 shows the resistive can type with 2 connection posts, while the 350 is a 3 wire connector with 5 volts, ground and output.
Ron
Forum: Engine Monitors 11-18-2021, 04:10 PM
Replies: 15
Views: 1,942
Posted By Cumulo
Amazon?

This may be helpful
I looked at the on-line manual for your monitor.
From that it looks like the type of oil pressure sender/transducer the EDM-350 uses is 5 Volt solid state of a common sort. So an...
Forum: RV-12/RV-12iS 10-31-2021, 10:14 PM
Replies: 10
Views: 2,891
Posted By Cumulo
Agreed. Once upon a time I had an FAA repair...

Agreed.

Once upon a time I had an FAA repair station. A 206 Stationair drove up and asked me to check out a comm problem. It was the stock factory set-up with 2 rather robust Cessna ARC...
Forum: Glass Cockpit 10-24-2021, 02:26 PM
Replies: 3
Views: 809
Posted By Cumulo
RF circuits

You can verify cables as not shorted using a ohm meter.
However, it is normal for many boxes and some antennas to measure near shorted with an ohm meter. Generally nothing to worry about.
Forum: RV General Discussion/News 10-23-2021, 08:30 PM
Replies: 46
Views: 5,939
Posted By Cumulo
Bob, GPS direction is a track, right? I think...

Bob, GPS direction is a track, right? I think that is what you meant.

I have used the method you describe for decades. Simple. As a practical matter, other factors will determine accuracy rather...
Forum: Glass Cockpit 10-19-2021, 11:53 AM
Replies: 15
Views: 2,183
Posted By Cumulo
Box

Wow. Looked at the video. The CDI is all over the place. There is no periodicity, just random wandering. So beat frequency and even scalloping is very unlikely. Did a lot of flying and a lot of...
Forum: Glass Cockpit 10-17-2021, 04:47 PM
Replies: 15
Views: 2,183
Posted By Cumulo
RPM

Might try changing RPM. Mag noise and propeller modulation of the signal can cause VOR waggle. Easy to check. Modern circuitry may have reduced it some. Used to be a common complaint.

Ron
Forum: Electronic Ignition Systems 10-12-2021, 01:55 AM
Replies: 29
Views: 4,260
Posted By Cumulo
Its density

My original assumption is right. Just density.
Found a straightforward document about "pressure" as it relates to spark ignition. Dan might like it. NACA 1920 report number...
Forum: Electronic Ignition Systems 10-10-2021, 04:32 PM
Replies: 29
Views: 4,260
Posted By Cumulo
Thank you, Ross, for your sage observations. Both...

Thank you, Ross, for your sage observations. Both you and Dan among others here are artisans in both talk and walk. Very few with that combo. Thx.

Re: the 20 bar pressure for 8.5 CR.
The...
Forum: Electronic Ignition Systems 10-10-2021, 12:34 AM
Replies: 29
Views: 4,260
Posted By Cumulo
75KV

You're keeping us hopping :) - had to review Paschen's Law. Wondering, though, where your 4 - for 4 atmospheres comes from. A 8.5 CR Lyc at full throttle should be up near 20 atmospheres. A CR of...
Forum: Electronic Ignition Systems 10-08-2021, 11:26 PM
Replies: 29
Views: 4,260
Posted By Cumulo
12v vs 400v

Dan's posts were quite good.

To the question of the difference of 12 volts verses 400 volts on the coil primary, BOTH inductive and capacitive systems produce a similar spike of a few hundred volts...
Forum: Propellers 07-29-2021, 08:29 PM
Replies: 14
Views: 3,103
Posted By Cumulo
Well, not really. But static RPM alone is a...

Well, not really. But static RPM alone is a pretty good test dyno. (free)
As was pointed out, late timing, low compression and I might add, flat cam, rich mixture can reduce power all with normal...
Forum: Flight Testing 05-11-2021, 03:43 PM
Replies: 24
Views: 6,582
Posted By Cumulo
Asymmetric flap experiment of yore

I once had a very nice BL75 Funk, a pretty good STOL a/c as it was. But since making things faster or in this case, slower, is in my nature, I set out to put some of my NACA reading to practice....
Forum: Glass Cockpit 03-20-2021, 08:32 PM
Replies: 7
Views: 1,332
Posted By Cumulo
well it has not been mentioned yet in this...

well it has not been mentioned yet in this thread, but regarding the test numbers by flipmick, the OP, the values described are actually impossible in theory.

If each of 2 points are 30 ohms to a...
Forum: Electronic Ignition Systems 03-08-2021, 01:04 AM
Replies: 22
Views: 7,182
Posted By Cumulo
robust design

Decades age I did design engineering. Down the hall was David Sun who became a zillionaire as Kingston Memory. Good for David. But I had the better real estate in the building though, a glassed in...
Forum: RV General Discussion/News 02-07-2021, 09:13 PM
Replies: 21
Views: 3,512
Posted By Cumulo
Ha. Or like a tuner that keeps calling a guy...

Ha. Or like a tuner that keeps calling a guy named Homer, Henry. Maybe may exhaust fumes? :)

I did the exhaust sys on an original 180 Lyc acro. It was 4 into nothing with 1 5/8 tubing. It sounded...
Forum: Alternative Engines 02-07-2021, 07:07 PM
Replies: 95
Views: 16,865
Posted By Cumulo
Yes

+1

Real numbers spoil everything.

Free Macro Assembly?
Forum: RV General Discussion/News 02-07-2021, 05:48 PM
Replies: 21
Views: 3,512
Posted By Cumulo
At ease. I think the error come from the way...

At ease. I think the error come from the way "cycle" is used in engine speak.

A cycle generally means a circle back to where one starts such as a yearly cycle of spring, summer, fall, winter.

In...
Forum: RV Building Tips/Techniques 01-25-2021, 11:50 PM
Replies: 14
Views: 2,237
Posted By Cumulo
Good question. Maybe have to ask GRT. A standard...

Good question. Maybe have to ask GRT. A standard location on many cert aircraft is poking out of the left side of the windshield as you said.

Impact air at SL at RV cruising speeds gives a pressure...
Forum: RV General Discussion/News 01-20-2021, 03:08 AM
Replies: 27
Views: 4,251
Posted By Cumulo
isentropic vs adiabatic expansion?

Expanding a gas through the blading of the inlet guide vanes of an axial compressor, which was one of your points, could possibly produce much more cooling effect than a throttle process..
I...
Forum: RV General Discussion/News 12-27-2020, 05:49 PM
Replies: 30
Views: 5,310
Posted By Cumulo
aerodynamics

Humm, a bottom mounted antenna that would serve that function could easily be designed. The gear leg is mentioned. Possible.

All of the trainer aircraft of WW2 that I am familiar with such as...
Forum: Propellers 12-24-2020, 12:45 PM
Replies: 40
Views: 8,987
Posted By Cumulo
With hat in hand, I'll offer this to the bright...

With hat in hand, I'll offer this to the bright group of people on this thread regarding torsional vibration. Higher compression ratios or advanced timing will make "peakier" power pulses. Though...
Forum: COMM 12-18-2020, 12:05 AM
Replies: 12
Views: 2,724
Posted By Cumulo
Agreed. Using a signal splitter to...

Agreed. Using a signal splitter to separate/combine the GS and VOR/LOC is a misapplication, a ~4db loss minimum and maybe a lot more. A good diplexer will be almost lossless for both bands .

Was...
Forum: Alternative Engines 12-16-2020, 02:14 AM
Replies: 81
Views: 13,271
Posted By Cumulo
Well, how about this? Hydrogen is here.

https://www.cnet.com/roadshow/reviews/2020-hyundai-nexo-review/

The Hyundia Nexo. Hydrogen fuel cell/ lithium battery. 161 HP, 291 ft lbs torque. Cool.

Buy one(~$60K), strip the motor, fuel cell...
Forum: Alternative Engines 12-14-2020, 10:29 AM
Replies: 81
Views: 13,271
Posted By Cumulo
won't happen

Bad, bad old arithmetic. It takes the fun out of everything, even my longing for an imagined quiet, comfortable electric airplane.

IC engine ~36% efficient (Carnot, another bad hombre in the world...
Forum: RV Ongoing Maintenance Issues 11-30-2020, 07:55 PM
Replies: 20
Views: 5,252
Posted By Cumulo
+1 I agree. Symptoms say sticking exhaust...

+1

I agree. Symptoms say sticking exhaust valve. Stuck intake will cause much more commotion. You have covered most other possibilities I believe.
Further, if an exhaust valve sticks and stays off...
Forum: RV General Discussion/News 11-30-2020, 03:38 AM
Replies: 12
Views: 2,805
Posted By Cumulo
Low pitch angle stop

Coupling the high idle speed and the fact that the a/c glides like a stone, it is most likely an unadjusted /mis-adusted low angle stop. Common rookie mistake.

Follow the approved data, of course...
Forum: Alternative Engines 11-24-2020, 04:53 PM
Replies: 63
Views: 12,368
Posted By Cumulo
Steve, you are correct. My first thought in...

Steve, you are correct. My first thought in reading the thread regarding putting the heat on the leading edge surface was that it would trip the boundary layer to turbulent. Maybe a skin radiator...
Forum: Traditional Aircraft Engines 11-24-2020, 02:45 PM
Replies: 17
Views: 2,723
Posted By Cumulo
+1 Yeah, Zero drop. Key switches have had their...

+1
Yeah, Zero drop. Key switches have had their probs with AD's, SB's. It would mean no ground on 2 positions.

The left-right temp is likely an indicator prob - grounds, etc. IMHO. Big temp diffs...
Forum: Traditional Aircraft Engines 11-24-2020, 02:13 PM
Replies: 17
Views: 2,723
Posted By Cumulo
I am stumped as well. The A&P card in my pocket...

I am stumped as well. The A&P card in my pocket doesn't help either. All of the clues point to mag timing being too advanced. But you have triple checked that to 25 deg, right? The amount of...
Forum: Alternative Engines 11-24-2020, 02:01 AM
Replies: 63
Views: 12,368
Posted By Cumulo
Even in theory, you can not get a zero drag heat...

Even in theory, you can not get a zero drag heat exchange from a skin radiator. Adding heat to the boundary layer will increase skin friction significantly. I think Hoerner covered this somewhat in...
Forum: RV General Discussion/News 11-14-2020, 06:51 PM
Replies: 25
Views: 7,096
Posted By Cumulo
Using Dan's very reasonable assumption of a flat...

Using Dan's very reasonable assumption of a flat torque curve at that rpm, tweaking the prop to get 2700 rpm will increase the power by 2700/2600 or 3.85%. Assuming power required at hi speed with...
Forum: RV General Discussion/News 11-12-2020, 12:37 PM
Replies: 62
Views: 13,209
Posted By Cumulo
Literally off the back of an envelope: at 200...

Literally off the back of an envelope:
at 200 mph, pressure rise ~5%, temp rise ~1.3% or
~7 degrees F.
I don't know what venturi effect is with an air scoop.
Forum: Propellers 10-24-2020, 08:09 PM
Replies: 14
Views: 5,874
Posted By Cumulo
Van's comment, etc

Some really good comments re fixed pitch, particularly Mr. Van G's on the front page with Propman and others in the thread.

I have used Javaprop to do light a/c prop design simulations for many...
Forum: Glass Cockpit 08-21-2020, 01:46 PM
Replies: 11
Views: 3,283
Posted By Cumulo
GTP-59 clone

In another thread I sketched out how to clone a GTP-59.
https://vansairforce.com/community/showthread.php?t=175216&page=2

The GTX is designed for a platinum RTD type temperature probe only. An...
Forum: RV General Discussion/News 08-07-2020, 12:18 PM
Replies: 13
Views: 7,026
Posted By Cumulo
I've read Sig Horner's DRAG cover to cover...

I've read Sig Horner's DRAG cover to cover several times, done wing section optimizing with Xfoil, etc.l and , so I am very familiar with the aero mechanisms at play here. I also find this subject...
Forum: Traditional Aircraft Engines 08-04-2020, 04:25 PM
Replies: 30
Views: 7,313
Posted By Cumulo
OK, troy ounce = 31.1034768 grams av. ounce =...

OK,
troy ounce = 31.1034768 grams
av. ounce = 28.3494 gram
pound = 453.592 grams
Forum: Traditional Aircraft Engines 08-04-2020, 04:13 PM
Replies: 30
Views: 7,313
Posted By Cumulo
Yes, that is certainly at least part of the...

Yes, that is certainly at least part of the answer. However, the major difference is actually proof that our process of compressing lead into gold is polytropic. At least, that is what my...
Forum: Traditional Aircraft Engines 08-04-2020, 05:52 AM
Replies: 30
Views: 7,313
Posted By Cumulo
Recipe for CR

Lotsa good Engine 101 here, but this post is more to the point of the OP's original query, garbled or not, for a chart relating compression ratio (CR) to some measurement.

Typically our aircraft...
Forum: Traditional Aircraft Engines 07-31-2020, 07:35 AM
Replies: 30
Views: 7,313
Posted By Cumulo
If instead, the OP is looking for clearance...

If instead, the OP is looking for clearance volume, the volume above the piston at TDC, the arithmetic is easy. ( Aero Mechanics High School, 1952)

Its Displacement / (CR-1).

So, for an O-360...
Forum: COMM 07-03-2020, 08:21 PM
Replies: 43
Views: 11,271
Posted By Cumulo
I don't want to discourage the use of the archer...

I don't want to discourage the use of the archer antenna, particularly on the nav side by what I've posted, Dale. I hate hair sticking out on aircraft, probably more than most. Using a BNC...
Forum: COMM 07-02-2020, 05:20 PM
Replies: 43
Views: 11,271
Posted By Cumulo
Certainly the Dynon box is not immune to very...

Certainly the Dynon box is not immune to very much EMI in older versions, and I agree, the most direct solution may be to upgraded it. But there is a bit of a gotcha with the Archer installation as...
Forum: RV-12/RV-12iS 06-25-2020, 03:25 PM
Replies: 360
Views: 482,376
Posted By Cumulo
To get through it , I had to add some paragraphs...

To get through it , I had to add some paragraphs to the aux tank recipe Interesting. Hmm. Maybe a 12.
r
Forum: COMM 05-28-2020, 11:54 AM
Replies: 10
Views: 1,675
Posted By Cumulo
Continuing with the cooking theme, aluminum foil...

Continuing with the cooking theme, aluminum foil is as good as a sheet or plate of aluminum electrically at 100 MHz. It can be quite handy for tests. Needs support, though.
Ron
Forum: Electrical Systems 03-04-2020, 12:06 AM
Replies: 17
Views: 3,736
Posted By Cumulo
Powersonic, which was mentioned earlier in this...

Powersonic, which was mentioned earlier in this thread has a quite good battery manual at: https://www.power-sonic.com/wp-content/uploads/2018/12/Technical-Manual.pdf .

It describes floating the...
Forum: Glass Cockpit 02-23-2020, 11:16 PM
Replies: 7
Views: 1,201
Posted By Cumulo
No. Same antenna. No box I know of can swap...

No. Same antenna. No box I know of can swap antennas for ILS. Maybe something amiss with the freg tuning of the ILS. Or maybe not. Your GS showed up, and the LOC and GS are paired. Hmm. Bad box or...
Forum: RV General Discussion/News 02-19-2020, 09:35 PM
Replies: 20
Views: 3,640
Posted By Cumulo
Yes, was a bit confused by the apparent...

Yes, was a bit confused by the apparent contradiction myself. Reread the far's, Fed Register.

Bottom line: The earlier 121.5 TOC91 is no new install. Later TSO C91A 121.5 unit is OK to install as...
Forum: COMM 02-18-2020, 01:59 AM
Replies: 10
Views: 2,625
Posted By Cumulo
As a guy who has designed a lot of circuitry,...

As a guy who has designed a lot of circuitry, waded around in waveguides, magetrons and other esoteric hardware for a long time, I think I've got the subject down pretty well. It has been my...
Forum: RV General Discussion/News 02-17-2020, 11:49 PM
Replies: 20
Views: 4,044
Posted By Cumulo
Thanks Bavafa That HF vac pump should work very...

Thanks Bavafa

That HF vac pump should work very well, maybe better than a football pump that I reversed the valve and piston in. It is good to have a reservoir. I made a vacuum tank from a large...
Forum: RV General Discussion/News 02-17-2020, 11:18 PM
Replies: 20
Views: 4,044
Posted By Cumulo
Good diagnosis by GalinHdz. My response would...

Good diagnosis by GalinHdz. My response would only apply if the static system of Newt' a/c was tight. Galin's assumption is more likely.

Newt's Q: ~Hardly any change when the alt static is opened...
Forum: COMM 02-17-2020, 08:10 PM
Replies: 10
Views: 2,625
Posted By Cumulo
Being well versed in the reciprocity rules of...

Being well versed in the reciprocity rules of radio communication, I am puzzled by the differentiation being applied to transmitting and receiving here. Transmitter protection circuitry kicking...
Forum: Alternative Engines 02-17-2020, 07:05 PM
Replies: 40
Views: 16,554
Posted By Cumulo
Wink Nostalgia

Thread made this old man look up Nikasil. Looks good. Requires diamond honing.

Bought an almost new Vega once with the engine parts in a box. Got a block with the stepped sleeves. Six on the...
Forum: RV General Discussion/News 02-17-2020, 06:06 PM
Replies: 20
Views: 4,044
Posted By Cumulo
Good question. It likely indicates a very well...

Good question. It likely indicates a very well sealed cabin area - if we are talking RV/low wing.

The pressure inside the fuselage will be the sum of all the openings to the outside and the...
Forum: RV General Discussion/News 02-17-2020, 04:47 PM
Replies: 20
Views: 4,044
Posted By Cumulo
Yep. Don't ask me Why I know. ron

Yep. Don't ask me Why I know.

ron
Forum: RV General Discussion/News 02-17-2020, 04:27 PM
Replies: 20
Views: 4,044
Posted By Cumulo
Quote: Originally Posted by Ironflight View...

Quote:
Originally Posted by Ironflight View Post:
A static leak into the cabin will cause airspeed to read high by maybe 10 knots (I?ve seen as much as 15) at cruise speed in RVs.



Ironflight...
Forum: Propellers 01-27-2020, 01:26 AM
Replies: 19
Views: 6,182
Posted By Cumulo
The two main competing factors which dictate a...

The two main competing factors which dictate a certain tip speed for maximum efficiency are: tip compressibility drag rise, and mass flow through the propeller disk.

We are generally stuck with a...
Forum: RV General Discussion/News 01-21-2020, 12:21 AM
Replies: 21
Views: 3,593
Posted By Cumulo
I did a static port mod years ago on a certified...

I did a static port mod years ago on a certified a/c to improve the airspeed accuracy, so I've been there.
The general effect of fore and aft location of the static port on the aft side of a low...
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