Van's Air Force
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RV-7A bad performance
- Thread starter MBISMAN
- Start date
Kahuna
Moderatoring
3 items to make power. Air, fuel, ignition.
Verify no air restriction.
Hows your fuel flow WOT max RPM?
Have you verified your ignition timing? How does the engine behave on each ignition alone?
How does your engine behave with the mixture control? Are you able to go from very rich to very lean and do all cylinders react accordingly?
Hows your compression test #'s?
Any chance you have an EFIS with some data?
Verify no air restriction.
Hows your fuel flow WOT max RPM?
Have you verified your ignition timing? How does the engine behave on each ignition alone?
How does your engine behave with the mixture control? Are you able to go from very rich to very lean and do all cylinders react accordingly?
Hows your compression test #'s?
Any chance you have an EFIS with some data?
RONSIM
Well Known Member
Just my opinion but
the only real measurement of airplane performance is TRUE AIRSPEED --- indicated airspeed, and ground speed are meaningless. Without TAS numbers at various power settings and altitudes, everything else is a WAG.
I guess my thinking is that indicated airspeed must always be corrected to TAS with temperature and pressure altitude. Groundspeed only reflects TAS with zero wind, which never happens in the real world. Sure, when you are going from point A to point B, groundspeed determines how long it will take. But, if trying to resolve an airplane (speed) performance issue, you must start from a finite point. I believe that has to be TAS determined at various power settings, altitudes, and airplane configuration.
the only real measurement of airplane performance is TRUE AIRSPEED --- indicated airspeed, and ground speed are meaningless. Without TAS numbers at various power settings and altitudes, everything else is a WAG.
I guess my thinking is that indicated airspeed must always be corrected to TAS with temperature and pressure altitude. Groundspeed only reflects TAS with zero wind, which never happens in the real world. Sure, when you are going from point A to point B, groundspeed determines how long it will take. But, if trying to resolve an airplane (speed) performance issue, you must start from a finite point. I believe that has to be TAS determined at various power settings, altitudes, and airplane configuration.
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Kahuna
Moderatoring
I would not bother messing with the filter itself unless you think it is severely contaminated. You said mixture does NOT react normally. Please explain.
53 liters/hr is 14gph which is plenty of fuel. We will assume this number is accurate.
"Lose 150t/mn with one centimeter rich poor. In this configuration the Lasar don't work it's the failure system by magneto witch work." I am not sure what this means. Translation issue?
If you are running WOT and the RPM is not exceeding its rated # to the engine, then no I do not expect there is any prop problem at all. A boat oar will do better than 130kts on a 360 running properly.
Give me these numbers:
RPM
MP
FF
Ground Speed
Altitude
He said it was ground speed which given all the work he has done, its unlikely he is getting that wrong. He is missing at least 30kts with the fairings off. We are talking huge numbers here.
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GLPalinkas
Well Known Member
Hi Mickael. Welcome to Vans Airforce. You will find your answer here. There are lots of knowledgeable and helpful people on this forum.
Kahuna is answering most of your questions and helping to diagnose the problem.
However, I would like to know how you are determining your airspeed? Which GPS unit and is it set up to read knots or are you converting the numbers?
I agree if you are burning 14 gallons per hour (53liters) at max rpm then something is wrong. You should be doing at least 160 knots without wheel pants.
Kahuna is answering most of your questions and helping to diagnose the problem.
However, I would like to know how you are determining your airspeed? Which GPS unit and is it set up to read knots or are you converting the numbers?
I agree if you are burning 14 gallons per hour (53liters) at max rpm then something is wrong. You should be doing at least 160 knots without wheel pants.
Are you absolutely certain the engine (ignition) is timed properly? Have seen a situation with a new plane I test flew once that had a retarded timing condition that resulted in slightly reduced power/speed. The A&P/IA multi-builder was certain the first time or two I asked him as well. It was retarded.
2300tr/MP23 32 litres 110/130kts 2000/4000ft
2400tr/MP24 36 litres 130kts max 4000/6000ft
2300tr/MP19 29 litres 130kts max 8000/10000ft
The mixture is Ok, I said: it's just necessary to lean mixture (level 0) for lose 150tr/mn to left or right magneto. If I don't lean mixture is this situation I lose more 150tr/mn and the engine don't turn normally. When I test left or right magneto, the Lasar light in board indicate that the electronic ignition is off and the engine turn with normal magneto. After few second, the light stop and the engine turn on electronic ignition. It's a security!
At 8000ft and 75% Van's indicate 172Kts, there is 42kts of more, perhaps 15kts for fairings, I lose 27kts!
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I realise he said it was GPS ground speed of 130 kt, but just in case he meant IAS I had the same problem ,my RV7A was indicating 20 mph low, it was a leak in the pitot line.
I also gained 20 mph with fairings
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lostpilot28
Well Known Member
First thing I would do is rule out the pitot/static system leak. Do a 3-way run, 120 degrees apart to cancel any wind. Average your ground-speed taken from GPS (on each leg), then compare that to the airspeed you recorded (again, for each leg).
Once that is done, then I'd start looking for mechanical problems.
Once that is done, then I'd start looking for mechanical problems.
Mike S
Senior Curmudgeon
Welcome to VAF!
Mickael, welcome to VAF
The Lasar requires a special tool to set the timing-----and the procedure must be followed correctly.
Good luck with your plane, pretty sure the VAF brain trust can sort this out for you.
Have you tried flying with another plane, which has an accurate airspeed indicator and comparing the two readings??
Mickael, welcome to VAF
The Lasar requires a special tool to set the timing-----and the procedure must be followed correctly.
Good luck with your plane, pretty sure the VAF brain trust can sort this out for you.
Have you tried flying with another plane, which has an accurate airspeed indicator and comparing the two readings??
Mickael, welcome to VAF
The Lasar requires a special tool to set the timing-----and the procedure must be followed correctly.
Good luck with your plane, pretty sure the VAF brain trust can sort this out for you.
Have you tried flying with another plane, which has an accurate airspeed indicator and comparing the two readings??
Yes certainly, I'm a turtle to 130kts in the community but for arrive to 130kts, I'm the best!
You have right, we arrive always to the Lasar system and there it's very difficult to find a specialist. Perhaps make a test with an other ignition system! Thank
It's possible, but I must make this with Lasar specialist and equiped. There is not a lot of specialist. Thank
Stevea
Well Known Member
As Mike Starkey said, you need a the right tool to time the LASAR system. A standard magneto timing box will not do the job. Specifically, you need a LASAR T-300 timing tool.
The LASAR system itself is no longer manufactured. I suspect the T-300 is also out of production. But, they do occasionally come up for sale here. I suggest posting a "want to buy a T-300 timing tool" note in the VAF Classified section. Someone on VAF may have one they are willing to sell to you.
The LASAR system itself is no longer manufactured. I suspect the T-300 is also out of production. But, they do occasionally come up for sale here. I suggest posting a "want to buy a T-300 timing tool" note in the VAF Classified section. Someone on VAF may have one they are willing to sell to you.
An very interessing answer: my RV7A have very good performance for take-of, perhaps too!
The Hartzell CS propeller supplied by Van's Aircraft is calibrated for every plane. I have this informations for my propeller, I would like to compare this values with an other owner of the same propeller. The model is: C2YR-1FBP-F7497. Thank very much for feedback information.
This informations are on the Hartzell inspection paper, it's the value of the Low and high pitch.
The Hartzell CS propeller supplied by Van's Aircraft is calibrated for every plane. I have this informations for my propeller, I would like to compare this values with an other owner of the same propeller. The model is: C2YR-1FBP-F7497. Thank very much for feedback information.
This informations are on the Hartzell inspection paper, it's the value of the Low and high pitch.
Is it cycling properly on your preflight? In other words, when you run the engine up to 1900 (or so) RPM with the prop full forward, and then pull the prop back, do you get a good RPM drop?
If the prop was staying in fine pitch for some reason, you'd effectively have a real good climb prop, but it wouldn't be great for speed.
When I test the CS in my preflight to 1800RPM, the RPM down but I push slowly the blue lever when the RPM arrive to 1500RPM. I don't know in this condition the exactly drop, but I can make a test next time. The take-off is always to 2700RPM at sea level, in mountain to 6500ft I can't put the full power at take-off for stay under 2700 RPM.
If you firewall the engine (full, open throttle) at takeoff, does your propeller control and maintain aprox. 2700 rpm?
The way I read your last sentence, you have to pull/reduce power to maintain 2700 rpm. If this is the case, it sounds like you have a propeller control problem of some sort.
You should be able to apply full power (regardless of altitude) and the propeller governor control the prop pitch, maintaining 2700 rpm.
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Internal timming?
I helped a friend several years ago with a very similar problem on his RV8. We had gone through many checks and tests before we came to this. I would have never guessed that an engine could run so well with the internal timming off one tooth but it will. A simple check can be performed in about 20 minuets.
First set the number one cylinder to TDC on the compression stroke.
Second, remove the rocker cover on the #2 cylinder and make sure both valves indicate closed. Move the prop in one direction you should see one rocker arm begin to move almost immediately. Rotate the prop back to TDC and try again in the other direction you should see the same on the other rocker.
If it takes several more degrees of movement on one side or the other from TDC to move a rocker you may be off a tooth in your accessory case causing a large loss in power. Easy to check. The only reason I might suspect this is the low time you indicated on your engine. It's an easy mistake to make during overhaul.
Ryan
I helped a friend several years ago with a very similar problem on his RV8. We had gone through many checks and tests before we came to this. I would have never guessed that an engine could run so well with the internal timming off one tooth but it will. A simple check can be performed in about 20 minuets.
First set the number one cylinder to TDC on the compression stroke.
Second, remove the rocker cover on the #2 cylinder and make sure both valves indicate closed. Move the prop in one direction you should see one rocker arm begin to move almost immediately. Rotate the prop back to TDC and try again in the other direction you should see the same on the other rocker.
If it takes several more degrees of movement on one side or the other from TDC to move a rocker you may be off a tooth in your accessory case causing a large loss in power. Easy to check. The only reason I might suspect this is the low time you indicated on your engine. It's an easy mistake to make during overhaul.
Ryan
I hate to tell on myself but I found an out of time PMag by doing a mag check at altitude. When doing a regular pre-flight mag check everything was fine. Although I got very little RPM drop. At altitude and cruise power I did a mag check only to find an increase in RPM when on one mag. It took me a while to figure this out but I knew it wasn't right.
The two mags were fighting each other. One more advanced than the other. Corrected my timing and now I get a 60 RPM drop during a mag check. Sure sounds like MBSMAN's problem is a prop that won't go course.
The two mags were fighting each other. One more advanced than the other. Corrected my timing and now I get a 60 RPM drop during a mag check. Sure sounds like MBSMAN's problem is a prop that won't go course.
BCP Boys
Well Known Member
Wow!!! Should put mine back on
Andy Hill
Well Known Member
If you slowly (say over 5 seconds) select full power on takeoff, what RPM do you reach?
If you rapidly select full power on takeoff (less than 1 second) what RPM to do you reach? And does it then reduce?
I appreciate you may not want to do literally what I say if the answer would be much more than 2700RPM, but even if the answers were "more than 2800RPM" etc. it would give a useful guide as to whether there is a prop / governor issue?
Yea, my comment may have lead off track but I thought he was saying he has to pull power at takeoff to stay below "2700". *Thought* he may also be pulling power at full power in flight. Bad line of thought/assumption.
Sure sounds like ignition or valve timing. But I'm just a voice on the Internet...
Sure sounds like ignition or valve timing. But I'm just a voice on the Internet...
Kahuna
Moderatoring
Couple of things next.
1. You said "Are you able to go from very rich to lean and do all cylinders react accordingly? No!" Please tell us what it does please. This will be a clue.
2. Timing. Id like to know if the timing was checked per the manufactures requirements.
3. If 2 is yes, Id pull a mag off and view the gear timing on all accessory gears per lycoming requirements.
4. Do you have an inductive timing light and do you know how to use it?
1. You said "Are you able to go from very rich to lean and do all cylinders react accordingly? No!" Please tell us what it does please. This will be a clue.
2. Timing. Id like to know if the timing was checked per the manufactures requirements.
3. If 2 is yes, Id pull a mag off and view the gear timing on all accessory gears per lycoming requirements.
4. Do you have an inductive timing light and do you know how to use it?
With these numbers I would check AS indicator and pitot system and cross check
GPS speed.
Also can you have someone with verified AS fly formation with you to check out.
This. I'd want to know what the GPS says on a speed run as well. My first guess reading this was that you have a pitot leak, or your pitot tube isn't aligned with the airflow properly.
Please don't take this the wrong way, but it would be difficult to impossible to check the internal gear timing from crank to cam by removing a mag. The simple check for this is to accomplish the test in post#22.
If the internal timing is off your mag can still be properly timed creating more confusion.
Ryan
rv7charlie
Well Known Member
Please check my math & specs for the engine.
This a/c full throttle sea level fuel flow is quoted as 53 liters/hr is ~14 gallons/hr.
180HP (sea level full throttle 2700 rpm, full power) should use
(180*.55 pounds)/6=16.5 gallons per hour, minimum.
In this a/c, full rich, 14gph/16.5gph= 84.8% power.
Can this a/c match Van's sea level climb rate at full power setting? (Full power climb rate should minimize aerodynamic drag influences to judge whether the engine is making full rated power.)
75% power on a 180 hp Lyc should be ~10 gallons (37.8 Liters)per hour, using 135*.45 lbs per hp per hr.
Quote from previous post:
At 8000ft and 75% Van's indicate 172Kts, there is 42kts of more, perhaps 15kts for fairings, I lose 27kts!
Unquote.
Van's numbers for 75% power at 8000 ft altitude assume wide open throttle and 2700 rpm, leaned for best power. (Fuel flow should be ~10gph; perhaps slightly less if the ignition advances for reduced manifold pressure.) What's the speed under those conditions?
Charlie
This a/c full throttle sea level fuel flow is quoted as 53 liters/hr is ~14 gallons/hr.
180HP (sea level full throttle 2700 rpm, full power) should use
(180*.55 pounds)/6=16.5 gallons per hour, minimum.
In this a/c, full rich, 14gph/16.5gph= 84.8% power.
Can this a/c match Van's sea level climb rate at full power setting? (Full power climb rate should minimize aerodynamic drag influences to judge whether the engine is making full rated power.)
75% power on a 180 hp Lyc should be ~10 gallons (37.8 Liters)per hour, using 135*.45 lbs per hp per hr.
Quote from previous post:
At 8000ft and 75% Van's indicate 172Kts, there is 42kts of more, perhaps 15kts for fairings, I lose 27kts!
Unquote.
Van's numbers for 75% power at 8000 ft altitude assume wide open throttle and 2700 rpm, leaned for best power. (Fuel flow should be ~10gph; perhaps slightly less if the ignition advances for reduced manifold pressure.) What's the speed under those conditions?
Charlie
Kyle Boatright
Well Known Member
The original poster indicated his airplane doesn't have the wheel pants installed. Are the gear leg and intersection fairings installed?
I would verify engine RPM. Get a digital tachometer and verify that the panel mounted tachometer is accurate.
I would verify engine RPM. Get a digital tachometer and verify that the panel mounted tachometer is accurate.
Kahuna
Moderatoring
Yes post 22 works fine. But a mirror, light, or any of our cheap cameras or bore scopes gets us the actual marks aligned without having to try and measure degrees moving a prop. That is not very accurate for the inexperienced.
10-15mph sounds like alot. just thinking outloud.
pierre smith
Well Known Member
Our 6A gained 16 MPH on a 4 leg course at 7500' and WOT, turning 2750RPM on a three-blade Catto, optimized for cruise speed, from 184MPH to 201MPH after all the fairings, including upper and lower intersection fairings (from fairingsetc). That's not at all unusual.
Best,
Best,
Jesse
Well Known Member
In en-10's we consistently gain 17kts when we add fairings (assuming the fairing brackets are on the mains without the fairings initially).
Confirm your GPS is accurate
There can be quite a variation between GPS velocity indications in the same vehicle. Hard to believe until you see it. My ipad is about 10 kts slow compared to my Garmin. I don't trust any of them until you test them for time over a known distance .
There can be quite a variation between GPS velocity indications in the same vehicle. Hard to believe until you see it. My ipad is about 10 kts slow compared to my Garmin. I don't trust any of them until you test them for time over a known distance .
It's probably the problem, I have an appointement with a specialist equiped with contr?ler T300 for check timing with precision. Thank
Mike S
Senior Curmudgeon
This is a good thing, it is either going to fix the issue, or remove one of the possible causes.........either way, it is something you need to do IMHO.
The timing was checked by a specialist who is not a specialist because he don't have the T300. It's probably the problem, I must verified this with an specialist of the Lasar Ignition system before other investigation. Thank
Interessing, I can see this with my mechanic, thank
