252 Cruise Speed

[Hank]

12 minutes ago, ArtVandelay said:

BTW, what’s the strip just in front of the windshield? Seems like that would cause drag.

Since it's a new Acclaim, it's probably known ice, so that would be alcohol spray for the windshield [or something else to keep it clear].

[aviatoreb]

4 hours ago, ArtVandelay said:

Anytime you put something on the front of an airfoil is going to cause drag, including the landing lights and dirt.From your picture they seem to recess the tks panels which should improve the airflow.

If it’s 10 knots slower I would say that is part tks, part VGs, and the extra antennas that wasn’t on the plane when measuring speed.

I assume if own a nice plane like that you keep it clean.

 

BTW, what’s the strip just in front of the windshield? Seems like that would cause drag.

 

Also, for those that didn’t look closely, the VGs span the entire wing...that’s like drawing a mustache on the Mona Lisa.

 

Tom

 

 

My general GUESS is that the flow is already ruined by the TKS so once it is ruined - meaning tripped so once it is tripped then the damage is already done as far as cruise is concerned and then no further damage is made by VGs but the VGS do give benefit of better slow speed maneuvering - slower stall and crisper slow speed handling.  But I do not know...

[M016576]

8 hours ago, Hank said:

Since it's a new Acclaim, it's probably known ice, so that would be alcohol spray for the windshield [or something else to keep it clear].

All TKS systems (FIKI and inadvertent) have that strip.  It’s a spray bar that sprays TKS on the windshield.

[Shadrach]

On 10/17/2017 at 7:05 PM, ArtVandelay said:

My JPI probes are, at least around 75°, I haven't check then at -40° which I think is their lower limit.

I just had a probe die a slow death. Numbers were erroneous for a few hours before dying completely. It still reads ambient but goes crazy and drops offline as soon an the exhaust gas hits it. I replace probes on condition. I’ve never noticed any degradation in performance other than failure. 

Edited February 13, 2019 by Shadrach

[PT20J]

On 10/20/2017 at 5:42 PM, milotron said:

I have had some issue with the bolted splice connections between the leads and wiring harness.Sometimes tough to get a good connection with them. In the milli volt range that these run in, it doesn't take much resistance to cause inaccuracy.

Make sure the star washer is between the two ring terminals per the JPI installation manual. 

[kortopates]

On 2/12/2019 at 8:53 PM, Shadrach said:

I just had a probe die a slow death. Numbers were erroneous for a few hours before dying completely. It still reads ambient but goes crazy and drops offline as soon an the exhaust gas hits it. I replace probes on condition. I’ve never noticed any degradation in performance other than failure. 

That's true about most probes - never any degradation in performance other than failure - especially CHT probes which will usually fail at the wire junction at the base of the probe. But EGT probes suffer from tip erosion and will tend to indicate lower than actual temperature when they get significantly eroded. Not a big deal for most since we don't tend to worry about absolute EGTs but it becomes important for those managing their TIT temps. 

The star washer between between the terminals is often overlooked by installers. But the biggest sin I see installers doing repeatedly is routing harness wires with ignition wires which adds considerably noise to the readings and I suspect its common because unsuspecting owners don't realize what they are missing out on without the noise. 

[DonMuncy]

I had one CHT probe go bad and read very high. So apparently they can fail different ways. 

I have always had problems understanding the necessity of putting the star washer between the terminals. It is hard for me to believe that one can't get a good connection between two terminals without it.  I suppose the star washers could "dig into" the terminals, and insure a better electrical connection. It is just strange that there are millions of electrical connections between two terminals with the lock-washer on the outside, that seem to work OK. (But I am still careful to put the star washer between, as specified.)

[Shadrach]

39 minutes ago, kortopates said:

That's true about most probes - never any degradation in performance other than failure - especially CHT probes which will usually fail at the wire junction at the base of the probe. But EGT probes suffer from tip erosion and will tend to indicate lower than actual temperature when they get significantly eroded. Not a big deal for most since we don't tend to worry about absolute EGTs but it becomes important for those managing their TIT temps. 

The star washer between between the terminals is often overlooked by installers. But the biggest sin I see installers doing repeatedly is routing harness wires with ignition wires which adds considerably noise to the readings and I suspect its common because unsuspecting owners don't realize what they are missing out on without the noise. 

Interesting and timely response. My lower plug ignition wires share a sleeve with the EGT and CHT harness. The probe that I thought had failed is alive and well again. The issue was actually that the #2 plug had gotten flakey. I thought it was loading up in the cool weather from doing circuits in the pattern, but the resistance was way out of spec. I replaced all of the lower plugs and the EGT was back on line the next time the engine was started.

Truth be told my ignition harness doesn’t owe me anything and may be a contributing factor. It looks and functions fine but is nearly 20 years old. It will be replaced next year at annual.

[ArtVandelay]

I had one CHT probe go bad and read very high. So apparently they can fail different ways. 
I have always had problems understanding the necessity of putting the star washer between the terminals. It is hard for me to believe that one can't get a good connection between two terminals without it.  I suppose the star washers could "dig into" the terminals, and insure a better electrical connection. It is just strange that there are millions of electrical connections between two terminals with the lock-washer on the outside, that seem to work OK. (But I am still careful to put the star washer between, as specified.)

Don,
I’m guessing it acts as a spring, providing a consistent contact and resistance, without it the vibration of wires could cause varying resistance and readings.


Tom

[kortopates]

2 hours ago, DonMuncy said:

I had one CHT probe go bad and read very high. So apparently they can fail different ways. 

I have always had problems understanding the necessity of putting the star washer between the terminals. It is hard for me to believe that one can't get a good connection between two terminals without it.  I suppose the star washers could "dig into" the terminals, and insure a better electrical connection. It is just strange that there are millions of electrical connections between two terminals with the lock-washer on the outside, that seem to work OK. (But I am still careful to put the star washer between, as specified.)

I believe its to prevent rotation of the two ring connectors, which then would lead to a loosening of connection. All other ring connectors on our Mooneys are mostly on a fixed terminal post that doesn't move unlike these two wires connected by a screw and in free space (not supported). Both rings are smooth and thus only tightness of the screw prevents them from rotating till the star washer is fitted between them.

Regarding the CHT probe going bad, the above points wasn't about different failure modes, that a whole other discussion topic, but about the fact most report accurate data till they fail in pretty obvious ways - typically with big fluctuations or very questionable indications. An EGT probes that dies from tip erosion are an exception is that you may notice TIT readings significantly higher with a new probe.

[PT20J]

On 3/2/2019 at 3:15 PM, DonMuncy said:

I have always had problems understanding the necessity of putting the star washer between the terminals

It’s possible for the plating on the ring terminals to oxidize over time and increase the contact resistance of the connection. The star washer digs into the plating for a better contact. If the terminals are tight, it most likely won’t really matter. Other connections on the airplane are in circuits much less sensitive to small voltage drops. 

[DonMuncy]

27 minutes ago, PT20J said:

It’s possible for the plating on the ring terminals to oxidize over time and increase the contact resistance of the connection. The star washer digs into the plating for a better contact. If the terminals are tight, it most likely won’t really matter. Other connections on the airplane are in circuits much less sensitive to small voltage drops. 

That makes some sense. With an ordinary lock nut situation, you are "digging" into only one of the terminals, or perhaps only into a flat washer, relying on the terminal surfaces to stay in electrical contact.