“Book Is Book” & Cessna Rigging

Note: There is a fantastic article on rigging with the Cessna Pilots Association. It can be accessed with membership to the association and is worth the cost of membership alone! What I am saying below was partially derived from this article. Tech Note No. 014 by John Frank & Steve Ells. https://cessna.org/

I had mentioned the concept of “Book is Book” on a post on BCP the other day with reference to Cessna speeds, which I thought I would elaborate on.

My experience is fairly deep, but not very wide, so my thoughts are generally centered around the Cessna 100 series (170s, 180s, 182s, and 185s.)

What I was referring to is the concept that a Cessna “should,” in a perfect world do what the engineers say it should do. If it doesn’t, you should try to figure out what is keeping it from this. A question was asked if the book at a certain setting and alt was 158mph, and a bird was doing 144mph, is this indicative of a problem? Of course the answer is, it depends…

First thing to keep in mind is that the “book” is an ideal number. This was most likely done on one really light “test” bird, on a prefect day. There are also installation errors to take into consideration like pitot interference, airspeed indicator accuracy, or a non level TB, so go into this with that understanding.

By no means is this an exact science, but the concept really comes down to do the speeds make sense. This is a critical thinking exercise.

There are a bunch of things that can slow a bird down, but we can break it down into five categories:

1) CG
2) Mods (like tires, antennas, ski fittings, etc etc etc.)
3) Age (tired motor, and to a lesser extent prop, or a different prop from “book”
4) Poor rigging
5) Damage

If you’re slow, you want to be able to reasonably point to the offending item. If not, don’t just be a passenger, do some digging.

(this is a quick rundown of my process, and I may be missing some stuff. Never the less…)

When I do a survey on a Cessna, the very first thing I do is a walk around. You can tell a TON about how it will fly based on how the presentation of the rigging is. Are the flaps sucked up where they should be? Do the ailerons match up with flaps? Where are the eccentrics set? Where is the rudder set? Are there any trim tabs on control surfaces?

I will also want to know about past damage. Fact is that ALL of these old birds have been prung to one extent or another. The question is how bad, and is it disclosed. I can’t tell you how many times I have talked to a seller on the phone who swears there is no damage Hx… I make the trip out to wherever the bird is only to point out evidence of one, two or even three past wrecks. If you know what to look for, you can find the fingerprints.

Not always true, but it is my experience that damage in the log usually translates into an ok flying bird, and damage not disclosed tends to present in a poor flying bird.

The next thing to do is see how it feels in flight. How fast, how slow, handling, heavy wing, etc… If she is flies nice and straight and is relatively close to book, then I move on. If there is a heavy wing, I know she has damage or needs a good rig. If she is slowish, I want to start finding out why.

Once back on the ground and armed with the feedback from the flight, I can start digging.

It’s important to get the bird on scales. For the most part, I have found that owners don’t want to know the true weight. We can debate this elsewhere, but from where I sit, the only one they are cheating is themselves. Most paperweights are wrong, very often over 100lbs wrong. The worst I have found was 400lbs wrong. Poor guy lost 400+ lbs in useful in an hour. (reason to do a good survey before you buy!) Aft CG is dangerous, but is fast. Most of these birds we are now all building have a FWD CG and this will slow us down… CG management is critical. On my bird, I went ahead and installed the later model tail spring and ABW tail head for CG management. The delta between the earlier parts and later parts is 4 lbs. At Sta. 262, this moved my CG in a better place and will give me a couple of tics on the AS indicator.

If you know you have good ## and CG data, the place to start is measuring the bird by doing a symmetry test. This consists of left to right, fore and aft. Digital level on the seat tracks gives you your baseline, and from there, measure the spars and then the horizontal stab and vertical to see if they are even.

Next, you want to do an airframe/wing alignment test. There is a rivet on the trailing edge of each wing, and a center rivet in the tail. You want to measure the distance between the two on the L and R to see if they are even. You also want to do this to the nose, and then from the outboard wing to the deck. This info gives you a clue as to if the bird is “square” or not.

Next, you should do an engine alignment test. Some engines are installed level to the fuselage, and some a nose down cant. Its important to see if the angle is where it is supposed to be.

Lastly, you want to measure the wing twist, or “washout.” This is done using a tool (you can easily make one) and a digital level. There are three spots to measure. Sta 39, Sta. 100.5, and Sta. 207. In a nutshell, the wings need to be parallel. The twist starts the strut (Sta 100) and should be 3 degrees.

Note: If your bird is prung, then the usual choice is learn to live with it or sell it. Some stuff can be fixed, but most damage that we find tends to be too expensive to address. This is always really bad news for an owner. They usually have bought the bird of their dreams and have already spent way too much in mods so the thought of selling is unthinkable. This again is why it is critical to have someone who really knows what they are looking for to help with a survey before you get in too deep.

Once you have ascertained the bird is perfect (wink) you move on to the rigging.

In my experience, I have found that most mechanics don’t know how to properly rig an airplane. Im not sure this is because they just don’t know how to do it, or because it takes so damn long (two day process…) but regardless, rigging is EVERYTHING!

In short, best thing to do is not to try to correct deficiencies bit by bit, but to take it back to stock. This is where most of the SNAFUs begin. A pilot comes in and complains of a heavy wing. His mechanic decides to droop a flap and let him go on his way. He might have helped the wing heaviness, but all he has really done is to induce drag. Wrong idea…

Cessna calls the procedure out clearly in the book. Eccentrics have a starting point. Flaps rods have a required length. Ailerons have a starting point. Bring the bird back to “stock,” and then go fly. If you have a heavy wing, try to work it out with the eccentric. If this doesn’t work, then there is something larger going on (damage.)

This said, we need to be realistic. These birds are old, and we know they have all suffered damage. If we cant get a bird to fly right with the eccentrics alone, then we may be forced to try other “cheats” due to the simple fact that rebuilding a wing may be just crazy talk. This is not wrong, just not perfect, and the perfect bird is a unicorn.

At any rate, I hope this is helpful. Bottom line is that it is ok if you are flying a slow bird… You just should know/understand why it is doing what it is doing. And, if a little elbow grease and attention to detail can pick you up 4 or 5 mph, than its worth it.

Side note, I first did this on my own Skywagon. It was apparently rigged by drunks, because I picked up a whopping 11 mph.

If anyone needs help or advice on this, or is interested in a good aircraft survey, feel free to shoot me an eMail.

Tis the Season…

There is a great new article up on BCP about ski flying by Mike Vivion.  Mike is a wealth of knowledge, and really does a lot for the community.  Thanks for taking the time Mike!  It’s definitely worth the read…


Cleveland Dbl Puck STC…

In case anyone needs it, here is the free STC SA63GL to run Cleveland 199-62 “double puck” breaks on a 180/185.

Download here: SA63GL


Cessna 185-27 Jackscrew Inspection Kit…

Just finished installing a 185-27 jackscrew inspection kit into an A185F.  It’s a real handy mod and a good thing to think about… Thought I’d post the install manual in PDF if it’s helpful to anyone.

Download here: SK185-27

Here goes nuthin…

I pulled my 470 and quickly sold my 470 back in November thinking I would only be down for a month or two, but after a long spring, I finally have some time on my hands, and am going to get my new motor back in the bird!  We finished the O-520 PPonk last month, and Im very excited to get it installed.

I took my time in the process, and hand painted each individual part before assembly.  The net result is a real pretty engine.

I took an IO-520F and used the PPonk STC to turn it into an O-520.  If you are unfamiliar with the PPonk mod, it takes a IO-520D/F, pulls off the fuel injection, adds low compression pistons, changes the fwd crossover tube, and adds a carb.  This mod will get you about 265HP.  http://pponk.com/

I ended up buying six brand Millennium new cylinders, but was surprised at the consistency out of the box.  In the end, we pulled them completely apart and got them perfect.   With a little care and obsessive attention to detail, she dyno’d at just under 300hp.  I’m hoping it’ll be screamer!  I also made the decision to run high comp pistons (legally by DER approval) so she should perform at altitude as well.

I’ll be running a 3 blade MT up front, and to avoid the chance of kickback and broken starter adapter, decided to go with a Shower of Sparks ignition.  This will retard the ignition during start and totally avoid a poor timing/kickback.

The plan will be to eventually pull out the non-impulse coupled mag and install the new Surefly electronic ignition.  This is a really cool unit that unlike the clunky Electro-Air is totally self contained inside the mag.  This combo (IMHO) will give the best of all worlds.  Surefly is hoping to have certification done by Oshkosh.  https://www.surefly.net/

I also decided to go with an old style starter adapter, and forgo a Skytec choosing an old skool energizer starter.  Yes its a couple more pounds back on the bird, but the piece of mind with that time honored starter is well worth it.

She was pretty much broke in on the test stand, so it should be fun right out of the box.  Big thanks to Tim at Unlimited Aero for the support.  http://www.unlimitedaeroengines.com/

CFI – Check

I guess I should toot my own horn for a second…  Finished up my CFI last month.  It was the hardest thing I have done in aviation, but for sure, the most rewarding!

If your interested in your tailwheel endorsement, or want some short field training, feel free to reach out.

Mountain Wave Aviation – Great Company

(unsolicited, but in a land where there is so much friction with service) I wanted to give a quick plug for Mountain Wave Aviation and its new owner Ron.

I have been installing the Mountain Wave nets on birds (as well as on my own buggy) now for 5 years, and have to say that I continue to be impressed with Ron and his customer service, not to mention the quality of the nets.

Folks that have tried to order nets in the past are familiar with their epic lead times… Sometimes over a year. Now that Ron has taken over the company, turn times are lightning fast.

If you want to learn more about the nets, go here: http://mountainwaveaviation.com

It takes a bunch of additional time and he would prefer not to do custom stuff, but I have also worked with Ron to create some of my own designs, and they have turned out awesome.

My favorite is the rear organizer pocket for the extended baggage.  Here are my sketches, and then the final net he made for me. I installed one on my bird as well as a customer’s bird that I just ferried out west.

If your looking for a cool new item to install in your Cessna, check out Ron’s rear carry thru or extended baggage net.  Well worth it!


Deja Vu Alaska

If you have a spare 35 min, this is a fantastic film that Zane just finished editing from our trip up to AK last spring.


Engine / MT Prop 4 Sale…

Now that I’m building the 520 for the Wagon, I’ll be selling the 470R and the 2 blade MT.   If you know anyone…






Here goes nuthin…


Finally have some free time so I’m diving in deep and starting in on the O-520F core that has been sitting in the corner of the shop.

I will be using the 2000hr TBO  PPonk STC with Millennium cylinders (venturi seats).  Should give some nice additional HP!  The engine is finally apart and the parts are going out for inspection and overhaul.


Hazards of Wildfire Smoke

Just read a nice article on the smoke this year out west written by Zane Jacobson…  Thanks to BCP.org for their steady production of backcountry content.  If you haven’t considered contributing, I urge you to support BCP with a small donation.



Knik Teaser…


Last May Zane Jacobson (from BCP.org) and I did some filming in AK while up at the Alaska Airman show.  The video is still in the edit room, but here is a short teaser that Zane cut together.

Brand New Beaver…

Seaplane Operators Look Out…

Not really sure what I think of this…. No pilots license needed???


Cessna 180 Certification…

Cool article.  Thanks to Mike Vivion for finding it!

Read the article here:

Aircraft Tundra Worksheet

I’ve noticed that there have been several folks looking for the Aircraft Tundra Tire Worksheet so here it is…

Also AC 23-17C

AK on the Brain… 170’s in the Wrangles

Feb is here, which means there is some chatter about this years Airman’s show… which got me revisiting old memories.  Watching Zane’s film of our 2014 trip really brings a smile.  Worth watching again, and if you haven’t seen it….


Thanks to Trent Palmer for posting the vid to Youtube!

Plug For Grypmat…


About a year ago a company called Grypmat reached out to me to test a new product they had… I did, and have come to find it invaluable when working on airplanes.  After some testing, I gave my feedback, which surrounded the mat’s issues with solvents and static charge.  To my astonishment, Tom (creator) listened and reformulated the mat.

Anyway, I just saw they have a Kick Starter campaign going to fund two more sizes.   After a year of using this thing, I feel strongly enough about the product that I wanted to support Tom.  FWIW,  I’ve funded $100 to their cause to get the two smaller sizes along with another 12×22.  If you haven’t seen them at Spruce or at OSH, give it a look.  Kudos Tom and good luck!

If you want to order a unit, I encourage you to consider funding their Kick Starter rather than ordering from Spruce.  To do so click HERE.


High Sierra Fly-In Article (BCP)

New article up on BCP about the High Sierra Fly-In.  Thanks to By and BCP for posting!