A straight technical approach to IAR 80, Mytha and reality

Hi everybody,

I have spent some time on this forum and finally I decided to join (if I am welcome). In principle I’ll be interested mainly in this unbelievable IAR80. I discovered this aircraft not so long and despite all the forum’s efforts, I still consider a lot of aspects unrevealed to the public. I believe that historic facts with the right technical corroboration and reverse engineering will generate accurate answers to a lot of questions and opinions. Although, many of the questions/opinions raised on this forum have simple engineering answers, present times computations, modeling and simulation are able to reveal amazing and unexpected aspects. I am willing to put some time/resources in this direction, as long as this is of interest. I need also to be supported with pertinent information. Nevertheless I saw other persons with technical background being active (especially someone working for a wind tunnel) and I’ll be happy to collaborate more closely with them.
To cut short a long story, I saw the general opinion about the lack of future possible developments after ’42 mainly because engine power. I am not sure if this is correct or not. However, I am sure that a technical investigation (not very demanding) can generate a good and trustable answer. This will be my first proposal to the community with the adequate request for support. Let’s find first in absolute value if the IAR K14 reached the limits at 1000 hp. Let’s find also how will look the real envelop performance of the IAR80 with a more powerful power-plant (IAR, BMW or whatever).
As a starting point let’s ask history’s help. Technical reports concerning failures and reparations might be a fortune. From what I am remembering the first engine generation was developing roughly 850 hp and in subsequent versions was pushed up to 1050. Can someone sort the failures reports per different variants? Let’s see the effects of an increased output power and to corroborate these effects with the relative modifications. A week point (if any) e.g. a sudden increase in valves failure, is already a very good start. After that, we can simulate the engine and to asset limitation. Information as bore/stroke compression is available (most probably) on line but real dimensions/weight/materials will be needed (at least with approximation). Any other detailed information e.g. timing, efficiency maps, etc are real helpful. My point so far is that IAR K14 with different combustion geometry / fuel and adequate supercharging can put at shaft much more power. Maybe I am wrong, maybe I am not. Anyways, this is a student level exercise and can be done in a matter of hours. Anyone interested to dump this myth?
Talking about envelope performances what was the exact top speed? It was 485/510/550 km/h? In what wing/weigh/engine configuration? In principle the behavior of ANY type of body (bluff or not) in an air stream follows the same rules. Typically is enough to know a point of functioning and extrapolation become enough precise. As an example, knowing a point of functioning e.g. 700 kW/5000m/2500kg/510 km/h it is possible to solve quite precise the mystery of maximum speed with an 801D engine. I remember someone saying that IAR engineers calculated around 600 km/h maximum speed with that engine. Well, so far this number doesn’t show right for aerodynamics. If the 510 km/h airframe will be preserved (plus 250 kg additional mass) the top speed is definitely under 600 km/h (1500hp). However, if the 550 km/h airframe is used, the top speed could be well beyond 600 km/h. Maybe let’s solve this mystery first (looks not complicate).

Another related issue is the airframe weakness/strength
I saw several opinions considering the airframe fragile. Well, from a historic point of view, if the operational reports are showing, let’s say 10% of the losses (or more) due structure failure/damage, most probably the airframe was at the limit. Is this the case? Do you have reports of this failures and were exactly this failure were occurred e.g. tail section, wing root etc? At the first glance (from the 80’s engineering plans posted here) the tail section looks quite strong. I can even say that is looking over-designed in some regards (although I don’t know details). This is just a formal opinion prior modeling and simulation. A different issue (apparently the same) is related to frame vibration caused by different engines. The fact that the Jumo engine caused dangerous vibration doesn’t means at all that the frame was fragile. This means only that a completely different engine (with different balancing) was not handled proper (from the NVH point of view). Is fair to say, that even today the NVH is not something very comestible and is far to be intuitive, therefore the IAR engineers are excused. However, someone mentioned here (maybe Victor?) that the DB 605 was also tested with great improvement in performances (an order was issued to DB for 200 engines but was not honored, or something like this). From what I know, the DB 605 has few hundreds extra horses over Jumo In my opinion this prove obviously that the frame (modified or not) was roughly good to handle much more power. Let’s solve right now this myth of extra power and (engine) frame reinforcement. A 2000 hp engine at full power driving a decent prop at 600 km/h develops less than 1000 kgf of thrust to the frame. How much is this 1000 kgf value? Well, if you compare it with a shopping cart is a lot. However, the power plant in a decent size car (as a BMW 5 series) can develop more thrust (tractive effort) in the first gear…. I Hope that now is clear that fitting a bigger engine may require frame modifications but the weight addition (which matter) is minor, definitely fewer than 100 kg. The NVH issue is different. This is an engineering knowledge which could (or not) be solved by IAR/BMW engineers. However, in absolute value can be solved with minor weight addition. The airframe reinforcement is a different issue too. By increasing the engine power, some maneuvesr might become forbidden in certain cases. However, the increase with 25% of the maximum speed in STRAIGHT and LEVELED flight is definitely not an issue for that class of aircrafts and most probably doesn’t require any airframe reinforcement.
It will be nice to study deeply these aspects with your help (and interest). Buy the ways, any other information about the DB 605 - IAR 80? I remember that I saw someone talking about a Hurricane retrofitted by the Romanians with a DB 605. Is a mistake or confusion? Does anyone can help?

For today should be enough. I’ll be glad to continue but this depends on your feedback
Anyway, the more I see the sleek IAR 80, the more I like it.
Congratulation for this great site!
CG Glijinski

Hello Glijinski, I am glad you decided to brake the silence It is a very interesting exercise and not so easy as it may seem from your reading, but if I can help in any way I would be glad to do it. Are you working with CFD (might be wrong but I think you might be an aviation engineer ) ?

This post has been edited by D13-th_Mytzu on February 25, 2008 10:24 pm

Any help is very welcome! If we are talking about CFD (in absolute value) you are perfectly right. CFD requires a lot of experience, computation power and software. Supposing that all these 3 issues are solved, still remain the issue of accurate information for calibration and validation purpose. At the first glance a CFD model should come with a 2mm margin of error to allow a 10 mm mesh size (at least for important parts of the wing). Do you believe that such kind of accuracy can be reach from the available information? Or prop/pitch/speed/engine data are available to calibrate air flow thru the 80’s radial engine and secondary effects e.g. manufacturing errors, rivets, paint etc? Nevertheless, just a comparative analysis with another aircraft e.g. 109 might be easier. However, a lot of answers do not require CFD and simple engineering calculation might generate enough accurate estimation. I believe that I had this point in my first post. Anyways, let’s try to move ahead and we’ll see what can/can’t be done.

I understood that 80’s top ace was (is) Dan Vizanty. I remember seeing a debate about his scores and I wonder if today after several extra years of research is any progress clarifying this matter. Anyways, if someone can post a picture with this brave airman I’ll fully appreciate. Thank you in advance,
CG

Yes, indeed. Cpt. av. Dan Vizanty apparently is the top scoring Rumanian I.A.R. 80/81 'ace'. According to my count, he was credited with 15+1 airplanes, counting at least 43 ARR victories.

I wrote a short biography of him, illustrated with a couple of portraits, in my book on Rumanian fighter aces, published by Osprey, in the UK, in 2003.

Gen. Dénes

This post has been edited by Dénes on February 27, 2008 07:18 pm

Glijinski I could also help with CFD (CAD model + computational power), I am the one working at the Subsonic windtunnel. Also, if you can immagine a clear program of research, I can help with other things. Denes, Victor, Cantacuzino, Dan Antoniu and others will most probably assist us in getting the technical data wee need - but I doubt we will be able to get a lot of details when it comes to technical data (hope I am wrong).
Friday I will leavea in a short holliday, after I come back I will be able to start working on this. Pls PM me a msn/ym contact where we can talk easier.
BTW: are you an aviation engineer ?

Thank you for confirming Cpt Vizanty as the top ace. Congratulation for such a book and I fully understand the copyright issue. However, I understood also that posting materials with the right references is allowed. Just I want to have a foretaste of the man-machine couple. No one can help?.

D-13-th Mytzu Thank you very much for offering your help. Is very encouraging to learn about common interests/curiosities/hobbies.

Despite your hesitations, very important technical data might come indirectly from collateral information. Reparation/maintenance manuals are also gold in term of technical information. Is hard to believe that hundreds of 80s were maintain in the duty line without manuals. I understood that several airplanes were used also as trainers after the war. The maintenance manuals should be somewhere… My suggestion is to start with the very first, namely the prop/engine assembly. At least let me familiarized with it. Let’s find what is myth and what is real. As an example let’s find if the maximum power was a correct number. I like to believe that IAR engineers developed the engines on a bench-test e.g Shenk water brake. However is not clear at all how they come with the power altitude correction. Did they have a barometric chamber and they real measured it, did they calculated (not trivial for a supercharged engine), did they sent the engine at DB for real measurement, etc? This will be a good starting point but I am opened for other suggestions.
I am sorry but I do not use anything like YM. I am not staying connected to Internet either. For any other matters please fell free to use gruspy@yahoo.co.uk
Have a nice holiday!
CG

Denes, I realized (with some lag) that you are an author and therefore you should be much familiarized with whatever was published in this field.
If you don’t mind, will you be so kind to suggest some titles/references? (focus on technical side). Anyone else is very welcome to share opinion and suggestions. Thank you in advance.

Make a list with the parameters you need for the simulation and we will try to find them.

The only comprehensive and reliable published source is the book of Dan Antoniu and George Cicos, titled Istoria unui erou necunoscut. IAR-80, by Modelism publishing house.

The book can be purchased directly from the publisher or the author. However, don't expect detailed technical specs., as only general technical information are included in the book.

Gen. Dénes

Thank you Denes,
I’ll be glad to order one and I’ll appreciate if you can tell me how. In the mean time I wonder if something is available in English or other international language. By the ways, the book you published in UK what language uses?
CG

Victor, thank you in advance for your help.

I’ll start with the engine but you have to teach me a lot of thinks. The single information I have are the drawings I retrieved from this forum. Although the drawings are explicative, many details are missing. First of all, teach me about the engine architecture. I see a 14 cylinder double row. But I can not see if the cylinders are spaced even or not. A well balanced engine has small variations between cylinder angles (few degrees) to compensate for the specific crank mechanism (has 1 master con and 6 slaves). However, many radials engines are only partial compensated. Also are possible variations between rows. The difference might be 10-20 hp (1-2%), therefore this is not mandatory information. I am not sure if between the engine and prop is a gearbox (something like a planetary one). Let me know what it is about.
Now mandatory stuff and I’ll start with the supercharger. I read about a supercharger but I could not identify it. If it is one, should be on the fuel tank side, most probably a centrifugal type. So please first confirm or infirm this supposition.
For a first thermodynamic simulation the minimum needed are: bore, stroke, con-rod length, compression ratio, valve timing, ignition timing, rpm, octane number and BOOST info - if did have a charger system. Will be good to know also generic materials e.g. aluminum pistons, cast iron liners etc to better estimate mechanic losses (can account up to 10% of the shaft power).
Let’s see what you can find.
CG

This post has been edited by Glijinski on February 28, 2008 08:56 pm

I am really curious if such information can be dug out from somewhere.. think this would be a good new research direction for Mr. Dan Antoniu

How exactly are you intending to simulate - basic calculations or you mean a computational simulation ?

This post has been edited by D13-th_Mytzu on February 28, 2008 09:04 pm

Queen's English.

Gen. Dénes

For this matter a computer simulation is much faster (and precise) than a hand calculation (if the models are already in place, which is the case). Will be my pleasure to share with the community whatever I’ll obtain.
Concerning the information there are several ways to obtain it. In 1940 CAD-CAM was not even SF. My first option will be technical drawings and should be something left. I can’t believe that all the execution drawings are lost. I am talking about what a simple lathe operator used daily. Most probably a pencil on (soiled)paper copied by a nice young girl from a designer’s drafting board. I’ll give an example why such kind of document is gold. Imagine the final piston machining. On that document are clear dimension of the piston main diameter (cylinder bore) and piston head. The difference between these two dimensions is needed to compensate for dilatation. Practically this difference is telling what maximum temperature was allowed for operation, which leads to many, many other information and estimations. Therefore a simple dirty, shredded pencil drawing can “talk” more than 2 weeks of super-computer simulation. Field manuals are also gold. Sorry but I have to go now. Next time (if you have the interest) I can continue.
All my best
CG