We’ve had a very good week. I started physiotherapy on Thursday, and now have a new set of exercises for my shoulder, wrist, leg and ankle. I’ll be going back for physio twice a week, and will be doing my exercises three times a day.

My right leg and ankle made huge strides this week. I had been walking around with crutches, placing partial weight on the leg. 10 days ago, I could support my full weight, but didn’t have enough ankle strength to keep myself from toppling over in a random direction if I didn’t steady myself with crutches. I exercised the leg and ankle every day, and it got stronger quickly. On Friday afternoon I took my first baby steps without crutches. I didn’t go far, and the ankle got tired very quickly, but it was a huge milestone.

Last night, I made it up the stairs to the master bedroom, and slept in our bed for the first time since the accident. Up to now I’ve been sleeping in a hospital bed in the dining room, on the ground level of the house. Today, we went to a big empty parking lot and I tried out the leg and ankle when driving our car - it went very well, including max effort braking. We’ve got a few scheduling issues to resolve, but I may get back to work for a few hours late this week. I’m pretty pumped to be getting closer to normalcy, one small step at a time.

Terry had a fairly good week. She is getting stronger every day, and is starting to learn what she needs to do to avoid pinching the nerves in her neck which gives her on again, off again pain.

A coworker and his wife came by today to weed Terry’s flower gardens. They have been by the last three weeks, and have almost got ahead of the weeds. Thanks.

I've had a pretty good week, but Terry's was quite mixed.

My ankle is getting a bit more capable each day. It has the strength to support most of my weight now, with some discomfort. But I still need crutches to provide balance, as the ankle doesn't yet have the strength and control it needs to keep me from toppling over in some random direction. The wrist is getting much stronger - now I can hold a five pound laptop computer horizontal, which was only a dream a week ago.

Wednesday it was quite nice, and Terry was feeling good, so we went out for lunch, and then did a quick visit to Chapters. We used to hit Chapters once or twice a month, but we probably hadn't been there since February. It was good to be back, if only for a few minutes (my foot swells if I spend too long in a standing position).

I had a visit with an orthopaedic surgeon on Thursday. It wasn't a completely satisfactory visit, as they were two hours behind schedule. They were effectively seeing two day's worth of patients in one day because all the appointments the week before had been cancelled. I didn't see my regular doctor, as another doc was helping out. He did give me clearance to start physiotherapy, so I made an appointment for a physio evaluation later this week.

Terry's week wasn't nearly as good as mine. Her back injury is healing well, but she is fighting a new issue. Some days are good, but on other days she has numbness in her hands, and significant pain in her arms and hands. She has had some tests done to figure out what the problem is, but they haven't found the smoking gun yet. The current theory is pinched nerves, but we don't know yet what the root cause would be.

We've booked airline tickets to fly to Green Bay, WI in late July. Terry will spend time with her sisters, and I will spend a few days at the EAA Fly-In at Oshkosh. I had hoped to fly the RV-8 there this year, but it will still be good to get there by car, so I can meet up with other builders. We've received a tremendous amount of support from the RV community after the accident, with lots of e-mails, telephone calls, and web forum postings, and it will do me a lot of good to see some of these great folks in person again. I doubt I'll be walking that well, so I'll probably end up renting an electric mobility cart.

We’ve had a pretty good week. My ankle is getting stronger and more flexible every day. I was supposed to have another visit with the orthopaedic surgeon on Thursday, but he had to cancel all his appointments that day, and it got rescheduled for this coming Thursday. I expect to start physiotherapy after that visit. I think I am getting close to the point where I could drive again, at which point I should be able to go back to work. We live out in the country, and the only practical way to get back and forth to work is to drive.

Terry’s torso is getting much stronger - she spends more time out of her back brace than in it. She was supposed to start physiotherapy this week, but her physiotherapist threw her back out, and had to cancel several days of appointments. Hopefully her appointment tomorrow will actually happen.

Friday at lunch time it was already quite warm, so we climbed in the car and did our first expedition all by ourselves. We had lunch, sitting outside at a local restaurant we like. It was wonderful to get out of the house, and to be able to do it without having to impose on someone else. Finally we are starting to get our freedom back.

I submitted my second Kitplanes article last week. The first article will be in the August issue, I think. The second article, if they like it, will probably be in the September or October issue.

The internet is like an old attic where you discover hidden treasures buried under old blankets. I was surfing the web, looking for something, and stumbled across an amazing archive of scanned performance data for 1940s fighter aircraft. You’ll find copies of flight test reports from many of the fighter aircraft used by Great Britain, the USA, Germany, and Japan during World War II. This includes the very earliest jets. We find such gems as:

• performance comparison of Spitfire Mk I vs Me 109E,
• Mosquito performance summary,
• performance comparison of many English and German fighters,
• combat evaluations of Zero, Wildcat, Hellcat and Corsair,
• P-80 performance trials, etc.

In short, it is a gold mine for anyone interested in World War II fighter aircraft.

It has been a good week. I’ve been doing several sessions a day of stretching the Achilles tendon, and then walking around supporting most of the right leg weight with crutches. I’m up to about 50 lb of weight on the leg now, and the ankle is feeling better than it was a few days ago.

Terry is still working through weaning herself off the back brace. The first few days, whenever the back brace was off she would feel extremely fragile, with it taking a lot of effort to ensure the back remained completely vertical. But yesterday and today, the muscles in her torso are obviously becoming much stronger, so that they are happy to support the back for up to three hours at a time. She starts physiotherapy tomorrow.

Today I got out to the Smiths Falls airport, to partake in the annual fly-in breakfast. Barry, an aviation enthusiast who lives close by, offered to drive me there and back. It was great to get back to the airport, talk with other club members, and to check on the aircraft. Thanks Barry!

I used the opportunity to dry out the desiccant plugs in the cylinders. I had planned to dry out my spare desiccant plugs at home yesterday, but I discovered that I had forgotten to bring them back from the hangar. Alfio, a local RV-9A builder, suggested that a halogen lamp could be used to dry the plugs out. I made some little tin foil “bowls”, and the halogen lamp dried out the plugs in about 45 minutes.

Terry had a big milestone today - she had her back brace off for a little while this morning and again this afternoon. It was really good to see her out of the back brace, even if only for a little while. The visit with her neurosurgeon went well yesterday. The X-ray showed the expected healing, so he gave her clearance to start weaning her self off the back brace. She will have it off for progressively longer periods each day, to allow the muscles in her torso to get used to having to work for a living again. On Monday she’ll start physiotherapy.

I’ve been working on stretching out the Achilles tendon so I can get enough range of movement in the ankle to allow normal walking. The range of movement is increasing, ever so slowly. Several times a day I spend a few minutes stretching, then hobble around, using crutches to limit the weight on the right leg. The ankle feels pretty ugly the first minute or two, then it starts getting warmed up and feels much better. I still have an awful long way to go, as I’m only up to about 25 lb of weight on the leg, and I can’t go for too far. But every day is better than the last.

The left wrist is working pretty well. It still doesn’t have quite the old range of motion yet, but it is pretty functional, and I can see improvement every week.

I need to make two more big milestones before I can go back to work. I need to be able to get up the stairs to the bedroom area by myself, and I need enough strength in the leg so I can drive. At the moment, we have an attendant car lady who comes by every morning to help us with the morning routine. She helps me get to the shower and back, but the schedule is such that by the time the whole morning routine is done it is pretty late to be leaving for work. I suspect Terry will be driving before me, assuming her back continues to cooperate.

All in all, we’re doing fairly well.

The basic method as described by Lycoming assumes the rpm is the same with mixture for peak EGT as it is at the fuel flow of interest. Thus the method, as described, is only workable for a constant speed prop, as the rpm will vary with fuel flow if you have a fixed pitch prop. I created a hypothetical extension to Lycoming’s method, that assumes that fuel flow will vary linearly with rpm for small changes of rpm at a constant MP, altitude and mixture control position. So, for example, if we have 2500 rpm and 10 gph at peak EGT, and 9 gph and 2400 rpm at the fuel flow of interest, I assume that if you could keep rpm constant, the fuel flow at peak EGT at 2400 rpm would be = 10 * 2400/2500 = 9.6 gph. Given that this calculation method is much less sensitive to errors in fuel flow at peak EGT as it is to fuel flows at the test condition, I think this approach will work for fixed pitch props.

I got some more power from fuel flow data today - this data was from Howard Handelman’s RV-7A with “Superior IO-360 Plus (roller lifters) 180 HP”, two mags and a Catto three blade fixed pitch prop. He got me four different fuel flows at about 2500 rpm at 7600 ft - one pretty close to peak power rich of peak EGT, and one at peak EGT and two more lean of peak EGT. I ran the data through the Lycoming power from fuel flow method, with the hypothetical addition to the method to make it work for fixed pitch prop. The variation of speed vs calculated power looks very good, which suggests that this power calculation method provides powers that vary correctly with fuel flow. If you look at the plot of Calculated Power vs CAS, you’ll see that all four points are very, very close to the line of perfect fit. This suggests that this method does a pretty good job of handling the differences in specific fuel consumption between rich of peak and lean of peak ops.

It is too early to declare victory yet, but the first two results are encouraging. Note: I don’t yet have a very good idea as to whether this method accurately calculates power. At the moment my investigation has focused on whether it provides a calculated power that varies correctly as the mixture varies. The question of whether it provides the correct power value is a more difficult one to answer. I hope to eventually have enough data to be able to compare the power values from the classical Lycoming power charts. But even that will not provide a definitive answer, as there are so few of our engines actually match a configuration that was delivered by Lycoming, so it is hard to find a good power chart to use for every engine.

Thanks Howard.

I had another visit with the orthopaedic surgeon yesterday afternoon. The X-rays and visual inspection showed the expected healing, so he gave me clearance to start putting partial weight on the right leg. He defined partial weight as 10 lb on day 1, increasing by no more than 10 lb a day, as the pain allowed. He said to stand supported by crutches, with the right leg on bathroom scales, and to calibrate my sense of what 10 lb felt like, then to walk around the house putting that much weight on the leg.

I was a bit disappointed, having been looking forward to getting clearance for partial weight on the leg, and sort of expecting that it would mean perhaps 50 lb. But, after trying the leg out this morning, I learned that 10 lb feels like a lot more than it used to, and that is about all the ankle is ready for right now. I spent a fair bit of time working on stretching the tendon that goes up the back of the calf, as at the moment I can just get the heel on the floor if the leg is at 90 degrees to the foot, but I need to be able to push the knee forward with the foot flat on the floor so I can walk. I either need to get that tendon stretched out, or start wearing high heels. :)

The right ankle is a bit sore right now from its exercise today, but I am happy to have passed to the next phase of the recovery.

The classical method to determine power from internal combustion aircraft engines is to use the power charts produced by the manufacturers. But, those charts are only valid if you have the mixture set for best power. Many people, especially those with fuel injected engines, prefer to cruise with the mixture leaner than the setting for best power, which means the power charts are useless.

Several years ago I stumbled across an ancient internal Lycoming document that describes a method to determine engine power based on fuel flow data. The method was supposedly usable at any mixture setting. It is laborious to use, requiring the user to look up values on multiple charts to correct for the ratio of fuel flow to fuel flow at peak EGT, compression ratio, rpm and engine displacement. If this method works, and is usable in the real world, I’ll document it and release spreadsheets and python scripts that simplify the use of the method.

I played around with this power determination method with my RV-8 before our accident, but never got enough experience with it to draw any conclusions. But even if it works well for me, with my aircraft, I wanted to know how well it would work for other people, on other aircraft. So I launched a “science project”, wrote up test cards with a test procedure, and asked other RV flyers to do some testing and send me data.

The big question I’m trying to answer is “does this test method yield a consistent calculated power at both rich and lean mixtures?” I will attempt to answer this question by having people fly cruise speed tests, gathering data at a wide range of fuel flows with constant altitude and throttle position. A study of how TAS varies with calculated power, both rich and lean of peak EGT, should give a good indication of how well this test technique works. Also, we can compare the calculated power at mixture for best power against the Lycoming power charts.

I put out the request for data on Sunday morning, and the first data arrived overnight Sunday night. So far I only have results from two different test points on one aircraft, but I am quite encouraged by how the power calculation method worked on that aircraft.

Webb Willmott sent me data from 2400 rpm, full throttle, at 8,500 and 10,500 ft, from his RV-7A, with Superior IO-360-B series engine.

The first two plots are IAS * calculated power vs IAS^4. In a perfect world, with perfect data, zero error in the airspeed system, constant prop efficiency, and a perfect way to calculate power, all points would fall on a straight line. The real world is not perfect, so we see some noise in the data. But the ROP and LOP points line up nicely, which suggests that this method of calculating power may be able to account for different mixture settings.

The next two plots are calculated power vs IAS. You can see that if we assume any of the points could have an error of one kt (which is a very small error, given the normal variations in speed) that all points fall within one hp of the fit line. Very encouraging.

Finally, I used standard methods to correct each test point to sea level, standard day, 1800 lb weight. In a perfect world, all points at all altitudes, temperatures, weights and power settings would fall on a straight line if you plotted TAS * calculated power vs TAS^4 (after correcting both speed and power to sea level, standard day, standard weight). We see that there is a small difference between the 8,500 ft and 10,500 ft test points after they were corrected to sea level conditions.

The discrepancy between the 8,500 ft and 10,500 ft points could be caused by any number of things. It could be due to errors in the power calculation method, errors in the fuel flow, errors in the OAT, errors in the IAS, errors in the weight, variations in prop efficiency, etc. I’m experimenting with hypothetical adjustments in all these inputs, to see which ones are the most likely source of the discrepancy.

I hope to get data from several more RVs, and will then make a decision on whether this power calculation method is worth pursuing. If it looks workable, I’ll write up an article for Kitplanes magazine, and release a spreadsheet and python scripts that do the calculation. I hope to explain how to use this power calculation method + a few hours of flight testing to produce cruise performance charts for your aircraft, valid with the mixture at either rich or lean of peak EGT.

Test Procedure

If any readers are interested in feeding me some data, the test procedure is as follows:

Before flight, ensure you know the aircraft weight by accounting for all the stuff in the cockpit and baggage areas. If the item wasn’t on the aircraft when the weight and balance was done, either remove it or figure out how much it weighs and account for in the gross weight. Fill the fuel tanks, and record the calculated gross weight with full fuel, all occupants, etc.

Find a test area with very smooth air, and no vertical air motion. No mountain waves, etc. Record the pressure altitude (i.e. with altimeter set to 29.92) and OAT. I don’t care what altitude you use, as long as the air is smooth and has no vertical motion.

Set the desired rpm and MP, and don’t change them for the duration of the test. Record the rpm.

Slowly adjust the mixture to find peak EGT, and record the fuel flow at peak EGT. Note: the test method assumes that all cylinders peak at the same fuel flow, but the real world doesn’t work like that. Ideally you would record the fuel flow when each cylinder peaked (i.e. record four or six fuel flow values). Or, if they all peak at about the same fuel flow, give me an eyeball average of the fuel flow at peak EGT for all cylinders. Don’t send just the fuel flow when the first cylinder peaks.

When looking for fuel flow at peak EGT, be very aware of how quickly or slowly your EGT system responds to changes in mixture. If your EGT system is slow to respond, you’ll need to be very patient when adjusting the mixture, to let the EGT stabilize after each change. Otherwise it is quite possible to record a too low fuel flow at peak EGT.

Without changing throttle position, prop control (constant speed prop) or altitude, record level flight IAS vs fuel flow for a wide range of fuel flow values, both ROP and LOP. The wider the range of fuel flows the better, as long as the engine is running smoothly, with no misfiring. At each fuel flow, wait long enough for the IAS to stabilize, which may take several minutes. Record fuel flow, fuel remaining, and IAS.

For extra brownie points, you could repeat the above at one or more different conditions. I.e. change one or more of the altitude, rpm or MP. Data from several different flights is OK, as long as the aircraft CG remains pretty much the same - i.e. if you have an RV-4 or -8, don’t do some flights with a passenger, and some without, as that will affect the relationship between power and speed.

Send me the following data:

Engine model Engine compression ratio Type of ignition system Prop type (I don’t need a detailed model number - I just need to know if it is constant speed or fixed pitch) Aircraft gross weight on the day of the test with full fuel. For each altitude, rpm and MP that you have data, send me: * Altitude * OAT * RPM, and * Fuel flow at peak EGT for each cylinder

Then, adjust the mixture to a wide range of fuel flows, both rich and lean of peak EGT. Wait at each mixture setting long enough for the IAS to stabilize, then record: * fuel flow * fuel remaining * rpm (only needed for fixed pitch prop), and * IAS

Remarks - I am particularly interested in the stability of your fuel flow indication. I.e., with constant rpm, MP, altitude, mixture control, how much does the fuel flow indication vary up and down? Knowing this will help me interpret any noise in the results - i.e. is the noise due to issues with the method to calculate engine power, or is it possibly due to uncertainty in the fuel flow data).

Test Cards

I created test cards for constant speed prop (pdf format) and fixed pitch prop (pdf format).

We’ve had a pretty good week. My left hand and wrist are working well within the range of motion that they have, and the range of motion is increasing a tiny bit each day. Just a few minutes ago I finally was able to touch my left thumb and little finger together for the first time in 10 weeks. It took everything I had, and they barely touched each other, but it is still a big milestone. My left ankle is pain free, and the range of motion is very slowly improving.

The wrist crutches I tried ten days ago weren’t useful to me, but another coworker delivered a set of armpit crutches a few days ago. I don’t think I could have used them two weeks ago, as the left collarbone was still giving me a bit of pain. But it has greatly improved in the last week, and I found that it didn’t complain about armpit crutches at all. The biggest issue is the poor circulation in my right ankle and foot. The foot starts to turn red within seconds of standing up, as the blood pools in there. I don’t think I should standup for too long, so I haven’t made any great use of the crutches yet. The poor circulation has me slightly concerned. I hope it improves quickly once I can start walking.

Yesterday evening Jim and Kim, two great friends who live close by, sprung us free from the house and took us to a local restaurant. We bought them dinner as a tiny recompense for all the assistance they have provided us since the accident. It was great to have a change of scenery, and the wonderful meal and bottle of wine sitting outside on the restaurant patio capped it all off. Thanks Jim and Kim.

I’ve got another doctor’s visit this coming Thursday, the 28th, and I hope he will let me start putting some weight on the right leg.

Terry is doing well. She has some occasional back pain, but not too much as long as she manages to restrain her urge to do things she shouldn’t