A straight technical approach to IAR 80, Mytha and reality

For opposite view I have only a picture and a
cross section drawing.

Compressor drawings and picture.

Excellent! The compressor drawings are very explicit (it's a beauty). The compressor wheel has straight blades and a model should be not a problem. I am waiting now for D13-th_Mytzu reply.
Thank you.
CG

So far I have the main information needed to start a thermodynamic engine model. I might have some results in a week or two. In the mean time I am looking for a way to introduce in the model the compressor behavior. The first choice will be a compressor map (if someone has it) but I doubt that even the GR engineers plotted it. The other choice is to simulate the compressor in CFD based on the good and accurate drawings posted here by Cantcuzino (thank you). I am still waiting an answer from D13-th_Mytzu in this regard. The compressor behavior is needed mainly to simulate the influence of altitude on the power output. By the way, I remember that I saw on a similar forum a comparison between DB605, Merlin and Allison but I don’t remember where. I’ll highly appreciate if someone can retrieve this piece of information (my memory doesn’t help anymore) to make some comparative analysis. I strongly believe that this type of analysis is very helpful to understand events like June 6th ‘44 . Despite many opinions I am slowly starting to believe that the 80 was superior in many regards to P 38 at low altitude. So far this is only a personal supposition but let’s have the analysis done to confirm/infirm it.
All my best to you
CG

This post has been edited by Glijinski on March 26, 2008 05:42 pm

I believe you are reffering to June 10th'44 events (not June 6th) where indeed IAR 81 C were superior to P-38 at low altitude.
The P-38 with large wing span (16m) were not so quick in aerobatics at low altitude (compressor boosting being useless).

You are perfectly right – June 10th with Cpt. Vizante in command.
When I’ll have more engineering back-up will be nice to have a detailed view about those events. Maybe a new topic? What do you think?
CG

Will be my pleasure

If i may, i'd like to resurface this thread, i've looked around and it's probably the closest to what i'd like to talk about.

Reading again through my IAR-80 books , i've always wondered why such a large difference in performace between No.1 and No.2 , during tests in 1940.

Aparently No.1 , with engine IAR K14 IV C-32 ser. 5001 and Zenith 1030 carburettor , fully equiped at a weight of 2583 kg, managed only a top speed of 485,6 km/h.

No.2 , fully equiped at 2648 kg( heavier ), engine serial 5002 and Zenith 550 RGSL carburettor, managed 524 km/h max , plus much faster climbing times.

I'm wondering, why such a big difference between the two in performance? Could the faulty VDM prop be at fault ? As an observation it seems that serial production engine have a yet another type of carburettor, the Zenith 130 RGSL. Not sure how much this affects the serial aircraft performance.

Now, absolutely no disrespect to the authors of the IAR-80 book, we should always be grateful for writing such a book ( never though i was going to see such a book when i was a kid and started learning about our IAR-80) but i think surely must be some sort of typografical error regarding that table with aircraft weight /performance / weapons etc at the end of the books ( both).

This subject was brought up before namely how come all the version have exactly the same max speed, 485km/h ? If you read the test reports at the beggining of the book and then read that table , it doesn't make much sense is it ?

Besides it states black on white in the book acording to official reports, removing just the armour of the aircraft in 1943 (probably reffering to armoured seat, windscreen , tanks protection etc ) would have gained 25km/h, so weight DOES have an apreciable effect on performance.

So unless i've made an eror somewhere, i personally believe that based on IAR-80 No.2 performance data ( which again it says in the book is the performance aproved by the MAM ), the figured in Modelism 1989-90 are closer to the truth, they just make more sense. Just my humble opinion.

So ...is there going to be anything new regarding this performance aspect in the AG03 book ,Radub ?

Thanks.

The airframe limitations and maximum speeds were specified in the technical manuals. In use, it is possible that some airframes never reached those parameters while others sometimed did. It is possible that some airframes were better/worse than others.
The speed increment that could be gained by removing the armour appears in an official report. We assume that whoever wrote that report had good reasons to believe it. So far, official reports and factory guidelines are all we have. I am not able to contradict them.
Hth
Radu

Absolutely , even two brand new aircraft straight off the production line it's possible they would have had slightly diferent performance , as with the engines too ( of course , they must abide by some tolerances , i assume).

So, to clarify this , the aircraft manuals say the top speed is only 485 km/h for an early variant ( IAR-80/80A ) ?

I'm just curious where did the performance figures published in 1989-90 Modelism come from.

From memory:

514km/h for IAR-80.

470km/h for IAR-81 with bomb and launcher (IAR-80 TMA book says the launcher itself reduces speed by 15km/h)

495km/h for IAR-80B.

470km/h for both ( i think) IAR-80C and IAR-81C -presumably with drop tanks(3030 and 3060 kg weight with DT respectively)

455km/h ( again i think ) for IAR-81A with 3 bombs.

Many thanks.

The excellent Modelism articles were written in 1988/1989. After 1990 access to archives was "relaxed". At that stage George Cicos compiled the data that appeats in the book he co-authored with Dan Antoniu. I have no other data that disputes or refutes these findings. We are still discovering new things about the IAR80/81, but right now this is all we have.
Hth,
Radu

Thanks for your input Radub, much apreciated, looking forward ( really forward !) to your book this autumn.