305 Rocket Review

[aviatoreb]

2 hours ago, cujet said:

It would have to be down 50+ HP to lose 18Kts. 

We would like to believe that all antenna are equal. They are not. Those VOR bar antenna you see on many aircraft are very high drag items. ADF is a bad one, if mounted externally. 

Very low drag antenna: 

Very high drag "towel bar" antenna:

 

I'm not claiming that a couple of antennas cause the 18Kt loss. But it's good to understand that book numbers often do not include any gross offenders. Let's put that another way, making book numbers often takes an amazing amount of effort, generally involving the removal of equipment and the optimization of all things drag related. 

An interesting example includes the Gulfstream GIV aircraft as originally designed. It was easily capable of far exceeding M0.88 (MMO) in cruise flight at FL410, even when heavy. Add in a properly faired Satcom antenna and it's radome on top of the tail and the maximum cruise speed drops to M0.85. Same altitude, same fuel flows, huge drop in cruise speed. Just one change that looks completely invisible to the casual observer. 

 

The common angled fiberglass covered VHF com and LORAN antenna each create about 4 pounds of drag at Rocket speeds.  12 pounds of drag, with 3 of those babies. Conversely, the blade style VHF antenna have 3/4 pounds of drag. 

 

The removal of the V antenna on a Bonanza is worth almost 3kts, and it's has only 2 pounds drag at Bonanza speeds. 

So what's the alternative to towel bar antenna?  ...other than the upcoming eventual decommissioning of the VOR system?  How much drag you say on a towel bar?

[carusoam]

How much drag at 17k’...

-a-

[cujet]

1 hour ago, aviatoreb said:

So what's the alternative to towel bar antenna?  ...other than the upcoming eventual decommissioning of the VOR system?  How much drag you say on a towel bar?

 

Unfortunately, I don't know the "towel bar" drag numbers. It ain't good though. Remember, there are variations on these too. Some are angled aft, for a reduction in drag. Some have larger bases. None are good. I "think" I remember reading 8 pounds, but my memory is useless, and I have no idea what speed the rating would be at. 

Lower drag alternatives include certain (but not all)  V shaped wire VOR ones or the higher end dual blade antennas, properly positioned with the local airflow

 

The trick question of the day is what Carusoam asked: "How much drag at 17k’... "  Since we are discussing a fast turbocharged piston aircraft that can achieve similar IAS at various altitudes, the drag will nearly the same at a given indicated airspeed, regardless of altitude. Not really identical, but for our discussion, that's close enough. 

 

One major reason Experimental aircraft go so fast is that builders tend to hide antennas, and keep all forms of drag and unnecessary weight to a minimum. 

Edited August 18, 2018 by cujet

[aviatoreb]

19 minutes ago, cujet said:

 

Unfortunately, I don't know the "towel bar" drag numbers. It ain't good though. Remember, there are variations on these too. Some are angled aft, for a reduction in drag. Some have larger bases. None are good. I "think" I remember reading 8 pounds, but my memory is useless, and I have no idea what speed the rating would be at. 

Lower drag alternatives include certain (but not all)  V shaped wire VOR ones or the higher end dual blade antennas, properly positioned with the local airflow

 

The trick question of the day is what Carusoam asked: "How much drag at 17k’... "  Since we are discussing a fast turbocharged piston aircraft that can achieve similar IAS at various altitudes, the drag will nearly the same at a given indicated airspeed, regardless of altitude. Not really identical, but for our discussion, that's close enough. 

  

One major reason Experimental aircraft go so fast is that builders tend to hide antennas, and keep all forms of drag and unnecessary weight to a minimum. 

One very expensive option for the towel bars is there is some kind of mod that places those antennae inside the plastic wing tips thus essentially eliminating them entirely from the wind.  I figure the VOR system will be gone in 5 years....

8lbs is quite a lot.  Hard to believe its that much...but they are quite round and big.

..right isn't the answer to Carusoam's question that the pounds of drag will be relatively the same at any given IAS (not TAS) at 17? (vs 7).

[ArtVandelay]

You can lookup the coefficient of drag for cylinders (approximates wire antennas), it’s independent of IAS. Cylinder shapes are very drag.

[aviatoreb]

21 minutes ago, teejayevans said:

You can lookup the coefficient of drag for cylinders (approximates wire antennas), it’s independent of IAS. Cylinder shapes are very drag.

Yes - I can.  And I can get out my caliper and measure my antenna.  And assume an infinite unobstructed wall.  And perhaps be within 25%.

or ask my middle son to do that for me which come to think of it he would do at a drop of a hat and probable I should.... he is a junior aero major.

or I thought someone might know the actual answer for these specific units on our airplanes.

Ill make up some numbers - cuz that’s what one does on the internet. Removal = 3kts for 5amu to hide them in the wing tips.  Better make it 3.26kits for $5424 since artificial precision is more convincing.  

Edited August 18, 2018 by aviatoreb

[EricJ]

11 hours ago, aviatoreb said:

I figure the VOR system will be gone in 5 years....

Unlikely, I think, since the GPS system is highly susceptible to jamming and other attacks.  The VOR system is apparently seen as the main backup to GPS navigation for aviation.   It's thinning, but only to a minimum level sufficient for navigation.   At least, that's my current understanding.

[cujet]

11 hours ago, aviatoreb said:

 

Ill make up some numbers - cuz that’s what one does on the internet. Removal = 3kts for 5amu to hide them in the wing tips.  Better make it 3.26kits for $5424 since artificial precision is more convincing.  

 

I'm really only trying to be helpful. I've done this before, once or twice, in the real world. 

https://www.adamsaviation.com/files/ww/Catalogues/RAMI.pdf

Edited August 18, 2018 by cujet

[aviatoreb]

1 hour ago, cujet said:

 

I'm really only trying to be helpful. I've done this before, once or twice, in the real world. 

https://www.adamsaviation.com/files/ww/Catalogues/RAMI.pdf

I must have come off snarky.  I was just having fun in guesstimating and honestly admitting I was guessing. Thanks for your link!

[aviatoreb]

1 hour ago, EricJ said:

Unlikely, I think, since the GPS system is highly susceptible to jamming and other attacks.  The VOR system is apparently seen as the main backup to GPS navigation for aviation.   It's thinning, but only to a minimum level sufficient for navigation.   At least, that's my current understanding.

I agree with you that the vor system should not go away but I think I read it may.

[Jerry 5TJ]

2 hours ago, EricJ said:

Unlikely, I think, since the GPS system is highly susceptible to jamming and other attacks.  The VOR system is apparently seen as the main backup to GPS navigation for aviation.   It's thinning, but only to a minimum level sufficient for navigation.   At least, that's my current understanding.

Well:

(1) GPS signal waveform is spread spectrum with potentially high resistance to jamming especially with directional and active jammer-nulling antennas.   A built-in upgrade path is to release the P code to commercial users, which will improve the jammer resistance by more than 10 dB and reduce the probability of spoofing attacks greatly.

(2) it is easy to jam an ILS or a VOR signal.   There is no jammer immunity designed into the 1940s waveforms.   Worse, the VOR system has no means of telling the user there is a degraded signal outside of the VOR site, so spoofing is not alerted.   The ground based system does self-check against internal failures, but unlike GPS ephemerides there's no system reportage.

Given how slowly the FAA "uptakes" new technology few of us have to worry about the VOR ILS system going away while we care. 

[kortopates]

15 hours ago, aviatoreb said:

So what's the alternative to towel bar antenna?  

My NAV antennas are buried in the wing tips. Originally I had a pair of Comant antenna's that went into a combiner that then spitted the signal to two radios. These were a pretty expensive and worked great. More recently I had to go to a smaller footprint when I changed out the control weights on my ailerons since the bigger Encore control weights would have interfered with the Comant antennas. After a lot research, I went with the same Bob Archer antenna's that he designed for LASAR to install in the LASAR wing tips and STC'd by LASAR. They only weight ounces and are really inexpensive compared to conventional Comant antenna's and actually work pretty well. My labor was the real cost of the project. You can still get these from Aircraftspruce - but not the  wing tips and STC.  Of course I was using my original Mooney wing tips but LASAR created their own wing-tip copy of the Mooney one to install on vintage Mooneys which included a buried nav antenna's option. They no longer offer them though. 

[EricJ]

34 minutes ago, Jerry 5TJ said:

Well:

(1) GPS signal waveform is spread spectrum with potentially high resistance to jamming especially with directional and active jammer-nulling antennas.   A built-in upgrade path is to release the P code to commercial users, which will improve the jammer resistance by more than 10 dB and reduce the probability of spoofing attacks greatly.

(2) it is easy to jam an ILS or a VOR signal.   There is no jammer immunity designed into the 1940s waveforms.   Worse, the VOR system has no means of telling the user there is a degraded signal outside of the VOR site, so spoofing is not alerted.   The ground based system does self-check against internal failures, but unlike GPS ephemerides there's no system reportage.

Given how slowly the FAA "uptakes" new technology few of us have to worry about the VOR ILS system going away while we care. 

I don't know whether it happens much in your neck of the woods, but in the SW the NOTAMs are filled with GPS outages while the military or whoever plays with jamming equipment.   Spread spectrum or not, anything can be jammed with sufficient noise power.   (Spent over thirty years as a wireless comm engineer, sometimes doing this exact sort of thing.)

In a VOR jamming attack your CDI will indicate loss of lock by loss of flag.   A spoofing attack may not be noticed, but jamming is easy to detect with a VOR receiver.   A VOR jamming attack would be less likely than a GPS jamming attack for a number of reasons, not the least of which is that most of the devices/systems/services somebody would like to disrupt (military navigation and targeting, financial transactions)  depend on GPS, while for the most part only civil aviation uses VORs.

Edit:  FWIW, GPS uses spread spectrum not so much for jamming immunity, but so that all the satellites can transmit on the same channel and the receiver only needs one channel.    

Edited August 18, 2018 by EricJ

[cujet]

So, after all this, where is that 18kts? 

My best guess is that it is a combination of drag increasing items. Each individual issue is minor in nature, yet they add up to a good bit of wasted time and fuel. 18kts loss over 4 hours is, quite simply, a big deal. That puts the slower airplane on a 70+ mile final when the other is on the ground. 

Worse yet, economy cruise is also affected negatively. 

[aviatoreb]

4 hours ago, kortopates said:

My NAV antennas are buried in the wing tips. Originally I had a pair of Comant antenna's that went into a combiner that then spitted the signal to two radios. These were a pretty expensive and worked great. More recently I had to go to a smaller footprint when I changed out the control weights on my ailerons since the bigger Encore control weights would have interfered with the Comant antennas. After a lot research, I went with the same Bob Archer antenna's that he designed for LASAR to install in the LASAR wing tips and STC'd by LASAR. They only weight ounces and are really inexpensive compared to conventional Comant antenna's and actually work pretty well. My labor was the real cost of the project. You can still get these from Aircraftspruce - but not the  wing tips and STC.  Of course I was using my original Mooney wing tips but LASAR created their own wing-tip copy of the Mooney one to install on vintage Mooneys which included a buried nav antenna's option. They no longer offer them though. 

Interesting.

How much time was the labor then?  You hid those little antennae  into your standard wing tips?  But are you saying that it can't be done anymore since there is a missing STC? Im probably misunderstanding you.

[kortopates]

2 hours ago, aviatoreb said:

Interesting.

How much time was the labor then?  You hid those little antennae  into your standard wing tips?  But are you saying that it can't be done anymore since there is a missing STC? Im probably misunderstanding you.

The Antenna's can be ordered from Spruce http://www.aircraftspruce.com/catalog/avpages/archer_antenna3.php?clickkey=5349125 For us already with Mooney wing tips its pretty easy. The only challenge is the approval since the only STC is through LASAR whom no longer sells their wing tip kit but was kind enough to allow me to use their STC. But if your A&P/IA is comfortable with it, one could install them as minor mod. The main labor is to carefully remove a dozen or two cherry max rivets from each wing tip to get them off, and to pull coax cable from the cockpit to the wing tips. Installing the actual antenna's isn't more than a couple hours. Re-installing the wing tips is also very quick except for touching up the heads with paint. Of course you'll want to add some time to remove the old tail nav antenna's and cover.

[M016576]

4 hours ago, kortopates said:

The Antenna's can be ordered from Spruce http://www.aircraftspruce.com/catalog/avpages/archer_antenna3.php?clickkey=5349125 For us already with Mooney wing tips its pretty easy. The only challenge is the approval since the only STC is through LASAR whom no longer sells their wing tip kit but was kind enough to allow me to use their STC. But if your A&P/IA is comfortable with it, one could install them as minor mod. The main labor is to carefully remove a dozen or two cherry max rivets from each wing tip to get them off, and to pull coax cable from the cockpit to the wing tips. Installing the actual antenna's isn't more than a couple hours. Re-installing the wing tips is also very quick except for touching up the heads with paint. Of course you'll want to add some time to remove the old tail nav antenna's and cover.

The new LASAR owner *seems to be* an innovative fellow based on all the emails, info he’s been putting out.  I’m willing to bet that he’d resuscitate that STC.. or maybe even consider modifying it so it could be more widely spread if we brought it to his attention.... any takers?  I’m ok investigating this if there’s enough interest....

that said- I’m pretty sure the difference in speed won’t be noticed on the ASI... at least not by me.  Kind of like the audiophile guys that say “these cables make everything sound Amazing!” Or the BMW guys that swear up and down that the undersized pulleys and induction kit make the car noticeable faster.  Maybe on a dyno- but not to me in practicality.

but I did buy the undersized pulleys... and the fancy cables... and the induction kit.  Maybe... just maybe... this time it will be different! Hah!

 

edit:  I did do one mod that made my plane noticeably faster... I sold my stock J and bought the missile.  That’s 30 knots and 150Lbs more useful load I do notice!

Edited August 19, 2018 by M016576

[Shadrach]

On 8/16/2018 at 11:02 AM, N201MKTurbo said:

no, it goes on your license

It is actually a Polish LIM-2

They could save money by running farm diesel instead of Jet A. Probably more refined than anything it burned before the curtain fell.

[M016576]

35 minutes ago, Shadrach said:

They could save money by running farm diesel instead of Jet A. Probably more refined than anything it burned before the curtain fell.

Hah! NATO code name?

[N201MKTurbo]

5 hours ago, Shadrach said:

They could save money by running farm diesel instead of Jet A. Probably more refined than anything it burned before the curtain fell.

Some of the jet boys have been known to run industrial kerosene. Either way it is illegal tax evasion.

[N201MKTurbo]

4 hours ago, M016576 said:

Hah! NATO code name?

Humm, it is not politically correct to use that word anymore.

Actually, the two seat trainer is called the “Midget”

The two seat trainer is the MIG-15UTI. The plane above is actually a SBLIM-2A

The engine is a Soviet copy of a British NENE 10. The museum has both on engine stands. We tried to take parts off of the Russian engine and put them on the British engine, but the Russian engine is all metric and the British is imperial.

Edited August 19, 2018 by N201MKTurbo

[kortopates]

12 hours ago, M016576 said:

he new LASAR owner *seems to be* an innovative fellow based on all the emails, info he’s been putting out.  I’m willing to bet that he’d resuscitate that STC.. or maybe even consider modifying it so it could be more widely spread if we brought it to his attention.... any takers?  I’m ok investigating this if there’s enough interest....

I am sure your are right. Its just that I'd bet most interested folks would already have tips and would just want to add antenna's. But with some interest I am sure they'd be game.

[Raptor05121]

On 8/13/2018 at 9:19 AM, Yooper Rocketman said:

No.  Rocket Engineering did an impressive job on the baffling (was even noted by the A&P conducting his first Rocket annual this year, under the watchful eye of one of the best IA's I have ever met).  When I sold my F model, the pilot was from Griffin GA and was Moonyized by his father who was the one that came up to Iron Mountain to look at it for purchase.  His dad asked if we would deliver it as he was concerned his son was not up to speed for a Mooney yet.  We did in April of 2000 and it was pretty hot the day we delivered it.  I let my hangar partner / E model Mooney owner / A&P/ best friend Steve fly the leg home in the Rocket and he tried the 2500 RPM/35" climb setting as we headed for the flight levels (I had been taught everything full forward until level off) and we started seeing temps getting to 400 degrees.  I told him go full throttle, full RPM and the temps came down immediately.  

One note on that (Steve); he has IMHO one of the nicest looking, fastest, and efficient E model Mooneys out there (155 knots, 8 gallons an hour, picture posted below).  He has more time in my Rocket over the last 5 years than his E, but has owned the E since the late 70's or early 80's.  He would take the Rocket in a heartbeat over his E. 

The fresh wash job was completed be me just before Oshkosh...........that's the kind of friend he is to me.

Tom

That is one GORGEOUS round-window. I believe that's the first 3-blade MT I've seen on a short body.  I love it!

[Shadrach]

On 8/19/2018 at 7:04 AM, N201MKTurbo said:

Some of the jet boys have been known to run industrial kerosene. Either way it is illegal tax evasion.

Throw some sprayers on it an you have a legitimate high speed aerial applicator.

[Hank]

5 hours ago, Shadrach said:

Throw some sprayers on it an you have a legitimate high speed aerial applicator.

Ooohh---chem trails!!!